cc: Remove the opaque rect return-parameter from ContentLayerClient.

cc/trees/layer_tree_host_pixeltest_on_demand_raster.cc

Index: cc/trees/layer_tree_host_pixeltest_on_demand_raster.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_on_demand_raster.cc b/cc/trees/layer_tree_host_pixeltest_on_demand_raster.cc
index 1553fa034dfe79d445487f7bc7702f0d5faa9f7c..80f5d21216d6f9d9685ea11d50cc9468f98efe7f 100644
--- a/cc/trees/layer_tree_host_pixeltest_on_demand_raster.cc
+++ b/cc/trees/layer_tree_host_pixeltest_on_demand_raster.cc
@@ -69,10 +69,7 @@ class BlueYellowLayerClient : public ContentLayerClient {
   virtual void PaintContents(
       SkCanvas* canvas,
       const gfx::Rect& clip,
-      gfx::RectF* opaque,
       ContentLayerClient::GraphicsContextStatus gc_status) OVERRIDE {
-    *opaque = gfx::RectF(layer_rect_.width(), layer_rect_.height());
-
     SkPaint paint;
     paint.setColor(SK_ColorBLUE);
     canvas->drawRect(SkRect::MakeWH(layer_rect_.width(),