Revert^2 "Enable String compression."

Test: m test-art-host (interpreter, JIT, AOT)
Test: m test-art-target on Nexus 6P (interpreter, JIT, AOT)
Test: Nexus 6P boots
Test: m ahat-test
Bug: 31040547

This reverts commit afcb365b2d3ae152989826c2afb0d98a9cf3f6be.

Change-Id: Id7e27d717c8e36d3c7abdde59ca2c8fd4fc221c9
diff --git a/runtime/asm_support.h b/runtime/asm_support.h
index c7a94a9..4a2e34f 100644
--- a/runtime/asm_support.h
+++ b/runtime/asm_support.h
@@ -246,7 +246,7 @@
 ADD_TEST_EQ(MIRROR_STRING_VALUE_OFFSET, art::mirror::String::ValueOffset().Int32Value())
 
 // String compression feature.
-#define STRING_COMPRESSION_FEATURE 0
+#define STRING_COMPRESSION_FEATURE 1
 ADD_TEST_EQ(STRING_COMPRESSION_FEATURE, art::mirror::kUseStringCompression);
 
 #if defined(__cplusplus)
diff --git a/runtime/image.cc b/runtime/image.cc
index 4e6da79..243051e 100644
--- a/runtime/image.cc
+++ b/runtime/image.cc
@@ -25,7 +25,7 @@
 namespace art {
 
 const uint8_t ImageHeader::kImageMagic[] = { 'a', 'r', 't', '\n' };
-const uint8_t ImageHeader::kImageVersion[] = { '0', '3', '8', '\0' };  // hash-based DexCache types
+const uint8_t ImageHeader::kImageVersion[] = { '0', '3', '9', '\0' };  // Enable string compression.
 
 ImageHeader::ImageHeader(uint32_t image_begin,
                          uint32_t image_size,
diff --git a/runtime/mirror/string.h b/runtime/mirror/string.h
index 35ce98e..dbb5a4c 100644
--- a/runtime/mirror/string.h
+++ b/runtime/mirror/string.h
@@ -32,7 +32,7 @@
 namespace mirror {
 
 // String Compression
-static constexpr bool kUseStringCompression = false;
+static constexpr bool kUseStringCompression = true;
 enum class StringCompressionFlag : uint32_t {
     kCompressed = 0u,
     kUncompressed = 1u
diff --git a/test/906-iterate-heap/expected.txt b/test/906-iterate-heap/expected.txt
index c8228d6..3e857ab 100644
--- a/test/906-iterate-heap/expected.txt
+++ b/test/906-iterate-heap/expected.txt
@@ -1,6 +1,6 @@
-[{tag=1, class-tag=0, size=8, length=-1}, {tag=2, class-tag=100, size=8, length=-1}, {tag=3, class-tag=100, size=8, length=-1}, {tag=4, class-tag=0, size=32, length=5}, {tag=5, class-tag=0, size=40, length=-1}, {tag=100, class-tag=0, size=<class>, length=-1}]
-[{tag=11, class-tag=0, size=8, length=-1}, {tag=12, class-tag=110, size=8, length=-1}, {tag=13, class-tag=110, size=8, length=-1}, {tag=14, class-tag=0, size=32, length=5}, {tag=15, class-tag=0, size=40, length=-1}, {tag=110, class-tag=0, size=<class>, length=-1}]
-15@0 (40, 'Hello World')
+[{tag=1, class-tag=0, size=8, length=-1}, {tag=2, class-tag=100, size=8, length=-1}, {tag=3, class-tag=100, size=8, length=-1}, {tag=4, class-tag=0, size=32, length=5}, {tag=5, class-tag=0, size=32, length=-1}, {tag=100, class-tag=0, size=<class>, length=-1}]
+[{tag=11, class-tag=0, size=8, length=-1}, {tag=12, class-tag=110, size=8, length=-1}, {tag=13, class-tag=110, size=8, length=-1}, {tag=14, class-tag=0, size=32, length=5}, {tag=15, class-tag=0, size=32, length=-1}, {tag=110, class-tag=0, size=<class>, length=-1}]
+15@0 (32, 'Hello World')
 16
 1@0 (14, 2xZ '0001')
 2
diff --git a/test/913-heaps/expected.txt b/test/913-heaps/expected.txt
index ff668df..e81cb9c 100644
--- a/test/913-heaps/expected.txt
+++ b/test/913-heaps/expected.txt
@@ -79,7 +79,7 @@
 5@1002 --(field@28)--> 1@1000 [size=16, length=-1]
 6@1000 --(class)--> 1000@0 [size=123, length=-1]
 ---
-[1@0 (40, 'HelloWorld')]
+[1@0 (32, 'HelloWorld')]
 2
 2@0 (15, 3xB '010203')
 3@0 (16, 2xC '41005a00')