Implement TextureImageTransportSurface using texture mailbox

content/common/gpu/client/gl_helper.h

Index: content/common/gpu/client/gl_helper.h
diff --git a/content/common/gpu/client/gl_helper.h b/content/common/gpu/client/gl_helper.h
index fd9f83a9cf047a49603cd9611d49d4e80105549a..bca5e051c5388bf056b23c431dfdc4694bc8c96d 100644
--- a/content/common/gpu/client/gl_helper.h
+++ b/content/common/gpu/client/gl_helper.h
@@ -16,6 +16,8 @@ class Rect;
 class Size;
 }
 
+class SkRegion;
+
 namespace content {
 
 // Provides higher level operations on top of the WebKit::WebGraphicsContext3D
@@ -65,6 +67,12 @@ class GLHelper {
   WebKit::WebGLId CompileShaderFromSource(const WebKit::WGC3Dchar* source,
                                           WebKit::WGC3Denum type);
 
+  // Copies all pixels from |previous_texture| into |texture| that are
+  // inside the region covered by |old_damage| but not part of |new_damage|.
+  void CopySubBufferDamage(WebKit::WebGLId texture,
+                           WebKit::WebGLId previous_texture,
+                           const SkRegion& new_damage,
+                           const SkRegion& old_damage);
  private:
   class CopyTextureToImpl;