force readbuffer clients to use specialized readFoo for flattenables

BUG=
R=mtklein@google.com

Review URL: https://codereview.chromium.org/26702002

git-svn-id: http://skia.googlecode.com/svn/trunk@11803 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkBitmap.cpp b/src/core/SkBitmap.cpp
index 434c817..63a760c 100644
--- a/src/core/SkBitmap.cpp
+++ b/src/core/SkBitmap.cpp
@@ -1610,7 +1610,7 @@
     switch (reftype) {
         case SERIALIZE_PIXELTYPE_REF_DATA: {
             size_t offset = buffer.readUInt();
-            SkPixelRef* pr = buffer.readFlattenableT<SkPixelRef>();
+            SkPixelRef* pr = buffer.readPixelRef();
             SkSafeUnref(this->setPixelRef(pr, offset));
             break;
         }