diff --git a/default.xml b/default.xml
index 638816a..c4cef71 100644
--- a/default.xml
+++ b/default.xml
@@ -2,69 +2,69 @@
 <manifest>
 
   <remote fetch=".." name="aosp" review="https://android-review.googlesource.com/" />
-  <default remote="aosp" revision="ndk-release-r21" sync-j="4" />
-  <project groups="presubmit" name="platform/bionic" path="bionic" revision="41488b79c440beb93202ac41fdd919d58feb3509" />
-  <project groups="presubmit" name="platform/development" path="development" revision="b481a6d729c854e50b6ad51549fa65338756397e" />
+  <default remote="aosp" revision="refs/tags/ndk-r21b" sync-j="4" />
+  <project groups="presubmit" name="platform/bionic" path="bionic" />
+  <project groups="presubmit" name="platform/development" path="development" />
   
-  <project name="platform/external/effcee" path="external/effcee" revision="b93cb2bdda93ed98f253b75a59582780c8460cc1" />
+  <project name="platform/external/effcee" path="external/effcee" />
   
-  <project name="platform/external/regex-re2" path="external/regex-re2" revision="84e28962b2c2f357b5daccb460501b169193fafe" />
+  <project name="platform/external/regex-re2" path="external/regex-re2" />
   
-  <project name="platform/external/libcxx" path="external/libcxx" revision="d73f343ced577c0f2f7c0380c01e7b52c7665e29" />
-  <project name="platform/external/libcxxabi" path="external/libcxxabi" revision="2fd58737987874cb4fea1c108abb210bb1d4380e" />
-  <project name="platform/external/libunwind_llvm" path="external/libunwind_llvm" revision="1dc6676dba152ac2a37ebd2610026452c1bda588" />
-  <project name="platform/external/llvm" path="external/llvm" revision="0c3d0c5bf04d62953fd1548ceff7d16a08e02953" />
-  <project groups="presubmit" name="platform/external/googletest" path="external/googletest" revision="6371bac034f56bcfe3d6a82a8de44b8905a12986" />
-  <project groups="presubmit" name="platform/external/python/cpython3" path="external/python/cpython3" revision="b0e85ca1ed410f0196f20f4c37d16dafd4878a3d" />
-  <project groups="presubmit" name="platform/external/shaderc/glslang" path="external/shaderc/glslang" revision="6fb634ba902146bb47646ef05a1974a144fb9feb" />
-  <project groups="presubmit" name="platform/external/shaderc/shaderc" path="external/shaderc/shaderc" revision="d113adb2c36feacc6e9d79ec9a25aa1cbbd79d01" />
-  <project groups="presubmit" name="platform/external/shaderc/spirv-headers" path="external/shaderc/spirv-headers" revision="7725f808292fc41f6ffa59aa399927a6d607a436" />
-  <project groups="presubmit" name="platform/external/shaderc/spirv-tools" path="external/shaderc/spirv-tools" revision="5ed58b4063b2d154553a4881f2cf41def423d33b" />
-  <project groups="presubmit" name="platform/external/vulkan-headers" path="external/vulkan-headers" revision="ffdba7a3a040b32843d8188c9d7c0f2d77311ba4" />
-  <project groups="presubmit" name="platform/external/vulkan-tools" path="external/vulkan-tools" revision="75992cfa407810b03676cd144cd3f33c776fd986" />
-  <project groups="presubmit" name="platform/external/vulkan-validation-layers" path="external/vulkan-validation-layers" revision="691254d74159549cf5ef8d2a69bb02c062b28a0c" />
-  <project groups="presubmit" name="platform/ndk" path="ndk" revision="7e5b7197dc4afd967f9e361ea1b994b9bc5fb6a8" />
-  <project name="platform/prebuilts/clang/host/darwin-x86" path="prebuilts/clang/host/darwin-x86" revision="fb6c691e05952000af217951b40449b88cf33ae8" />
-  <project groups="presubmit" name="platform/prebuilts/clang/host/linux-x86" path="prebuilts/clang/host/linux-x86" revision="a575b3396573e92d5b20ce3ff2431cd6b9eb7529" />
-  <project name="platform/prebuilts/clang/host/windows-x86" path="prebuilts/clang/host/windows-x86" revision="5abd8c2060a827597d0e01fcf2fff8f582887c8d" />
-  <project name="platform/prebuilts/cmake/darwin-x86" path="prebuilts/cmake/darwin-x86" revision="f3bfe547014d2d751b7547ad7847a51b0ea34dc8" />
-  <project groups="presubmit" name="platform/prebuilts/cmake/linux-x86" path="prebuilts/cmake/linux-x86" revision="da4b9cb08341185e002c8a8c5df73533cdb93b41" />
-  <project groups="darwin,arm" name="platform/prebuilts/gcc/darwin-x86/aarch64/aarch64-linux-android-4.9" path="prebuilts/gcc/darwin-x86/aarch64/aarch64-linux-android-4.9" revision="a89c9e0f736c4e3f6b3dc618e248ee4e56419c2a" />
-  <project groups="darwin,arm" name="platform/prebuilts/gcc/darwin-x86/arm/arm-eabi-4.8" path="prebuilts/gcc/darwin-x86/arm/arm-eabi-4.8" revision="6d08ca9f45ff685648fd13c75bf5cac4b11c19bb" />
-  <project name="platform/prebuilts/gcc/darwin-x86/arm/arm-linux-androideabi-4.9" path="prebuilts/gcc/darwin-x86/arm/arm-linux-androideabi-4.9" revision="ad7ca83cbab137cda64f8701ba9cda6a766a3197" />
-  <project groups="darwin" name="platform/prebuilts/gcc/darwin-x86/host/headers" path="prebuilts/gcc/darwin-x86/host/headers" revision="4ac4f7cc41cf3c9e36fc3d6cf37fd1cfa9587a68" />
-  <project groups="darwin" name="platform/prebuilts/gcc/darwin-x86/host/i686-apple-darwin-4.2.1" path="prebuilts/gcc/darwin-x86/host/i686-apple-darwin-4.2.1" revision="ec5aa66aaa4964c27564d0ec84dc1f18a2d72b7e" />
-  <project groups="darwin,x86" name="platform/prebuilts/gcc/darwin-x86/x86/x86_64-linux-android-4.9" path="prebuilts/gcc/darwin-x86/x86/x86_64-linux-android-4.9" revision="7f937857faf2ed865a19e83e08ace05c82e82c57" />
-  <project groups="presubmit,linux,arm" name="platform/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9" path="prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9" revision="c2885c755bd673681f24fdaf09f2886fbbdc9775" />
-  <project groups="presubmit,linux,arm" name="platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.8" path="prebuilts/gcc/linux-x86/arm/arm-eabi-4.8" revision="26e93f6af47f7bd3a9beb5c102a5f45e19bfa38a" />
-  <project groups="presubmit" name="platform/prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9" path="prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9" revision="e3cfd463c4e720e7bdf50f7d314ffa023695a11f" />
-  <project groups="presubmit" name="platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.15-4.8" path="prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.15-4.8" revision="d9aafaade740ca38612c742f6d87debf362132ea" />
-  <project groups="presubmit" name="platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.17-4.8" path="prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.17-4.8" revision="639243dd5cb2c5ea1313f033c75c8c533813a484" />
-  <project groups="presubmit" name="platform/prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8" path="prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8" revision="9c28f035f27080768be11a265aa64fb70924ed90" />
-  <project groups="presubmit,linux,x86" name="platform/prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.9" path="prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.9" revision="9d8e2e019e5013800ee0adfaffc328f61834ca44" />
-  <project groups="presubmit" name="platform/prebuilts/ndk" path="prebuilts/ndk" revision="ade9c05fdf040239b85794264a1c8c96635f7e7b" />
-  <project name="platform/prebuilts/ninja/darwin-x86" path="prebuilts/ninja/darwin-x86" revision="00f798346dedb4a7a6a6dcc9ad32ff09d66ee0db" />
-  <project groups="presubmit" name="platform/prebuilts/ninja/linux-x86" path="prebuilts/ninja/linux-x86" revision="6369b19fc3fbe765636af75d394627e2b92599ed" />
-  <project groups="darwin" name="platform/prebuilts/python/darwin-x86/2.7.5" path="prebuilts/python/darwin-x86/2.7.5" revision="0c5958b1636c47ed7c284f859c8e805fd06a0e63" />
-  <project groups="linux,presubmit" name="platform/prebuilts/python/linux-x86/2.7.5" path="prebuilts/python/linux-x86/2.7.5" revision="53add29eb7b4eaa9e128e3ec84eac9e65cf4c986" />
-  <project name="platform/prebuilts/renderscript/host/darwin-x86" path="prebuilts/renderscript/host/darwin-x86" revision="a0ede5664b4741348c0b6c8d5da06d483dcf2876" />
-  <project groups="presubmit" name="platform/prebuilts/renderscript/host/linux-x86" path="prebuilts/renderscript/host/linux-x86" revision="68a0a1ddacb81c97d718f46ad464a3851d0b67af" />
-  <project name="platform/prebuilts/renderscript/host/windows-x86" path="prebuilts/renderscript/host/windows-x86" revision="5df9f20565e63906167c82f6120c78e969b3b467" />
-  <project groups="presubmit" name="platform/prebuilts/simpleperf" path="prebuilts/simpleperf" revision="c7ad29abf1ac7e988299c0db87be7f84a909065a" />
-  <project groups="presubmit" name="toolchain/binutils" path="toolchain/binutils" revision="6f40a53b210eb1743939972b8a7dbdccb606f1f3" />
-  <project groups="presubmit" name="toolchain/build" path="toolchain/build" revision="58be6006bb71abb97d7cdff7be3e73d55bbc22b8" />
-  <project groups="presubmit" name="toolchain/cloog" path="toolchain/cloog" revision="604793eab97d360aef729f064674569ee6dbf3e1" />
-  <project groups="presubmit" name="toolchain/expat" path="toolchain/expat" revision="40172a0ae9d40a068f1e1a48ffcf6a1ccf765ed5" />
-  <project groups="presubmit" name="toolchain/gcc" path="toolchain/gcc" revision="a9d5e6fb22fe3283eeecfb97211a12c072a7b469" />
-  <project groups="presubmit" name="toolchain/gdb" path="toolchain/gdb" revision="04217dfddb2237b5bcec707f147458e2e3414ba9" />
-  <project groups="presubmit" name="toolchain/gmp" path="toolchain/gmp" revision="b2acd5dbf47868ac5b5bc844e16d2cadcbd4c810" />
-  <project groups="presubmit" name="toolchain/isl" path="toolchain/isl" revision="0ccf95726af8ce58ad61ff474addbce3a31ba99c" />
-  <project groups="presubmit" name="toolchain/make" path="toolchain/make" revision="0e5088b737c763044b8d125b5c018b6e75f0c5a9" />
-  <project groups="presubmit" name="toolchain/mpc" path="toolchain/mpc" revision="835d16e92eed875638a8b5d552034c3b1aae045b" />
-  <project groups="presubmit" name="toolchain/mpfr" path="toolchain/mpfr" revision="de979fc377db766591e7feaf052f0de59be46e76" />
-  <project groups="presubmit" name="toolchain/ppl" path="toolchain/ppl" revision="979062d362bc5a1c00804237b408b19b4618fb24" />
-  <project groups="presubmit" name="toolchain/python" path="toolchain/python" revision="8f08b1835d6dd123282c612b0702cc0ceb3e2640" />
-  <project groups="presubmit" name="toolchain/sed" path="toolchain/sed" revision="45df23d6dc8b51ea5cd903d023c10fd7d72415b9" />
-  <project groups="presubmit" name="toolchain/xz" path="toolchain/xz" revision="ac90d9b11e02bd6837917f7e981ed40dc2cb7d1b" />
-  <project groups="presubmit" name="toolchain/yasm" path="toolchain/yasm" revision="7a28367b72cb1e1667b081d6404afbd063898e70" />
+  <project name="platform/external/libcxx" path="external/libcxx" />
+  <project name="platform/external/libcxxabi" path="external/libcxxabi" />
+  <project name="platform/external/libunwind_llvm" path="external/libunwind_llvm" />
+  <project name="platform/external/llvm" path="external/llvm" />
+  <project groups="presubmit" name="platform/external/googletest" path="external/googletest" />
+  <project groups="presubmit" name="platform/external/python/cpython3" path="external/python/cpython3" />
+  <project groups="presubmit" name="platform/external/shaderc/glslang" path="external/shaderc/glslang" />
+  <project groups="presubmit" name="platform/external/shaderc/shaderc" path="external/shaderc/shaderc" />
+  <project groups="presubmit" name="platform/external/shaderc/spirv-headers" path="external/shaderc/spirv-headers" />
+  <project groups="presubmit" name="platform/external/shaderc/spirv-tools" path="external/shaderc/spirv-tools" />
+  <project groups="presubmit" name="platform/external/vulkan-headers" path="external/vulkan-headers" />
+  <project groups="presubmit" name="platform/external/vulkan-tools" path="external/vulkan-tools" />
+  <project groups="presubmit" name="platform/external/vulkan-validation-layers" path="external/vulkan-validation-layers" />
+  <project groups="presubmit" name="platform/ndk" path="ndk" />
+  <project name="platform/prebuilts/clang/host/darwin-x86" path="prebuilts/clang/host/darwin-x86" />
+  <project groups="presubmit" name="platform/prebuilts/clang/host/linux-x86" path="prebuilts/clang/host/linux-x86" />
+  <project name="platform/prebuilts/clang/host/windows-x86" path="prebuilts/clang/host/windows-x86" />
+  <project name="platform/prebuilts/cmake/darwin-x86" path="prebuilts/cmake/darwin-x86" />
+  <project groups="presubmit" name="platform/prebuilts/cmake/linux-x86" path="prebuilts/cmake/linux-x86" />
+  <project groups="darwin,arm" name="platform/prebuilts/gcc/darwin-x86/aarch64/aarch64-linux-android-4.9" path="prebuilts/gcc/darwin-x86/aarch64/aarch64-linux-android-4.9" />
+  <project groups="darwin,arm" name="platform/prebuilts/gcc/darwin-x86/arm/arm-eabi-4.8" path="prebuilts/gcc/darwin-x86/arm/arm-eabi-4.8" />
+  <project name="platform/prebuilts/gcc/darwin-x86/arm/arm-linux-androideabi-4.9" path="prebuilts/gcc/darwin-x86/arm/arm-linux-androideabi-4.9" />
+  <project groups="darwin" name="platform/prebuilts/gcc/darwin-x86/host/headers" path="prebuilts/gcc/darwin-x86/host/headers" />
+  <project groups="darwin" name="platform/prebuilts/gcc/darwin-x86/host/i686-apple-darwin-4.2.1" path="prebuilts/gcc/darwin-x86/host/i686-apple-darwin-4.2.1" />
+  <project groups="darwin,x86" name="platform/prebuilts/gcc/darwin-x86/x86/x86_64-linux-android-4.9" path="prebuilts/gcc/darwin-x86/x86/x86_64-linux-android-4.9" />
+  <project groups="presubmit,linux,arm" name="platform/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9" path="prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9" />
+  <project groups="presubmit,linux,arm" name="platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.8" path="prebuilts/gcc/linux-x86/arm/arm-eabi-4.8" />
+  <project groups="presubmit" name="platform/prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9" path="prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9" />
+  <project groups="presubmit" name="platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.15-4.8" path="prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.15-4.8" />
+  <project groups="presubmit" name="platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.17-4.8" path="prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.17-4.8" />
+  <project groups="presubmit" name="platform/prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8" path="prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8" />
+  <project groups="presubmit,linux,x86" name="platform/prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.9" path="prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.9" />
+  <project groups="presubmit" name="platform/prebuilts/ndk" path="prebuilts/ndk" />
+  <project name="platform/prebuilts/ninja/darwin-x86" path="prebuilts/ninja/darwin-x86" />
+  <project groups="presubmit" name="platform/prebuilts/ninja/linux-x86" path="prebuilts/ninja/linux-x86" />
+  <project groups="darwin" name="platform/prebuilts/python/darwin-x86/2.7.5" path="prebuilts/python/darwin-x86/2.7.5" />
+  <project groups="linux,presubmit" name="platform/prebuilts/python/linux-x86/2.7.5" path="prebuilts/python/linux-x86/2.7.5" />
+  <project name="platform/prebuilts/renderscript/host/darwin-x86" path="prebuilts/renderscript/host/darwin-x86" />
+  <project groups="presubmit" name="platform/prebuilts/renderscript/host/linux-x86" path="prebuilts/renderscript/host/linux-x86" />
+  <project name="platform/prebuilts/renderscript/host/windows-x86" path="prebuilts/renderscript/host/windows-x86" />
+  <project groups="presubmit" name="platform/prebuilts/simpleperf" path="prebuilts/simpleperf" />
+  <project groups="presubmit" name="toolchain/binutils" path="toolchain/binutils" />
+  <project groups="presubmit" name="toolchain/build" path="toolchain/build" />
+  <project groups="presubmit" name="toolchain/cloog" path="toolchain/cloog" />
+  <project groups="presubmit" name="toolchain/expat" path="toolchain/expat" />
+  <project groups="presubmit" name="toolchain/gcc" path="toolchain/gcc" />
+  <project groups="presubmit" name="toolchain/gdb" path="toolchain/gdb" />
+  <project groups="presubmit" name="toolchain/gmp" path="toolchain/gmp" />
+  <project groups="presubmit" name="toolchain/isl" path="toolchain/isl" />
+  <project groups="presubmit" name="toolchain/make" path="toolchain/make" />
+  <project groups="presubmit" name="toolchain/mpc" path="toolchain/mpc" />
+  <project groups="presubmit" name="toolchain/mpfr" path="toolchain/mpfr" />
+  <project groups="presubmit" name="toolchain/ppl" path="toolchain/ppl" />
+  <project groups="presubmit" name="toolchain/python" path="toolchain/python" />
+  <project groups="presubmit" name="toolchain/sed" path="toolchain/sed" />
+  <project groups="presubmit" name="toolchain/xz" path="toolchain/xz" />
+  <project groups="presubmit" name="toolchain/yasm" path="toolchain/yasm" />
 </manifest>
\ No newline at end of file