stop calling SkBitmap::flatten

src/core/SkWriteBuffer.cpp

Index: src/core/SkWriteBuffer.cpp
diff --git a/src/core/SkWriteBuffer.cpp b/src/core/SkWriteBuffer.cpp
index cca7d8170ac52684b94ae4bf846fe43419bb03c5..f2be41b266b612207bc1222e4291feafa96fb1d1 100644
--- a/src/core/SkWriteBuffer.cpp
+++ b/src/core/SkWriteBuffer.cpp
@@ -206,9 +206,8 @@ void SkWriteBuffer::writeBitmap(const SkBitmap& bitmap) {
         }
     }
 
-    // Bitmap was not encoded. Record a zero, implying that the reader need not decode.
-    this->writeUInt(0);
-    bitmap.flatten(*this);
+    this->writeUInt(0); // signal raw pixels
+    SkBitmap::WriteRawPixels(this, bitmap);
 }
 
 void SkWriteBuffer::writeTypeface(SkTypeface* obj) {