Fix the issue that it may get wrong stride in cc::ResourceProvider::MapImage.

cc/resources/resource_provider.cc

Index: cc/resources/resource_provider.cc
diff --git a/cc/resources/resource_provider.cc b/cc/resources/resource_provider.cc
index e58ed0b73b7c33c01b62ae654d8ec3bdf1664704..46cf4f26e9fb3316de9b997dbb2730e07d753670 100644
--- a/cc/resources/resource_provider.cc
+++ b/cc/resources/resource_provider.cc
@@ -2150,10 +2150,14 @@ uint8_t* ResourceProvider::MapImage(const Resource* resource, int* stride) {
     DCHECK(resource->image_id);
     GLES2Interface* gl = ContextGL();
     DCHECK(gl);
+    // In Android, the on-going SurfaceTexture based GpuMemoryBuffer can
+    // only get the exact stride after it is mapped. So it should call
+    // MapImage() first and then call GetStride().

[reveman, 2014/03/03 16:57:48]

No need to leak details of the implementation into this code. "MapImageCHROMIUM
must be called prior to GetImageParameterivCHROMIUM." is enough.

[junj, 2014/03/04 11:11:23]

Done.

+    uint8_t* pixels = static_cast<uint8_t*>(
+        gl->MapImageCHROMIUM(resource->image_id, GL_READ_WRITE));
     gl->GetImageParameterivCHROMIUM(
         resource->image_id, GL_IMAGE_ROWBYTES_CHROMIUM, stride);
-    return static_cast<uint8_t*>(
-        gl->MapImageCHROMIUM(resource->image_id, GL_READ_WRITE));
+    return pixels;
   }
   DCHECK_EQ(Bitmap, resource->type);
   *stride = 0;