Decouple the SkFlattenable from SkReader32/SkWriter32.

The current impl for SkFlattenable read/write buffers is 
that they extend from SkReader32 and SkWriter32, but that
dependency must be abstract if we are to add any other
serialization format.
Review URL: https://codereview.appspot.com/5999045

git-svn-id: http://skia.googlecode.com/svn/trunk/gyp@3654 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/core.gyp b/core.gyp
index c60059e..5cab78a 100644
--- a/core.gyp
+++ b/core.gyp
@@ -87,6 +87,8 @@
         '../src/core/SkMatrix.cpp',
         '../src/core/SkMetaData.cpp',
         '../src/core/SkMMapStream.cpp',
+        '../src/core/SkOrderedReadBuffer.cpp',
+        '../src/core/SkOrderedWriteBuffer.cpp',
         '../src/core/SkPackBits.cpp',
         '../src/core/SkPaint.cpp',
         '../src/core/SkPath.cpp',