Blend TextureLayer background-color at draw time.

cc/output/gl_renderer_draw_cache.h

Index: cc/output/gl_renderer_draw_cache.h
diff --git a/cc/output/gl_renderer_draw_cache.h b/cc/output/gl_renderer_draw_cache.h
index 85369ef0ac5e5cf5165669bbb2d305a19b2aace8..81b88673343ac3bce4ca73829ec57317012b476f 100644
--- a/cc/output/gl_renderer_draw_cache.h
+++ b/cc/output/gl_renderer_draw_cache.h
@@ -35,12 +35,14 @@ struct TexturedQuadDrawCache {
 
   // Information about the program binding that is required to draw.
   int uv_xform_location;
+  int background_color_location;
   int vertex_opacity_location;
   int matrix_location;
   int sampler_location;
 
   // A cache for the coalesced quad data.
   std::vector<Float4> uv_xform_data;
+  std::vector<Float4> background_color_data;
   std::vector<float> vertex_opacity_data;
   std::vector<Float16> matrix_data;