Don't create render passes for transparent images.

cc/delegated_renderer_layer_impl.cc

Index: cc/delegated_renderer_layer_impl.cc
diff --git a/cc/delegated_renderer_layer_impl.cc b/cc/delegated_renderer_layer_impl.cc
index 8528edf647fd47a2cff4426cf9a79e68944c213e..e3ff8d08237fc38423cdd91f2125a42c2f4e7038 100644
--- a/cc/delegated_renderer_layer_impl.cc
+++ b/cc/delegated_renderer_layer_impl.cc
@@ -22,16 +22,6 @@ DelegatedRendererLayerImpl::~DelegatedRendererLayerImpl()
     clearRenderPasses();
 }
 
-bool DelegatedRendererLayerImpl::descendantDrawsContent()
-{
-    // FIXME: This could possibly return false even though there are some
-    // quads present as they could all be from a single layer (or set of
-    // layers without children). If this happens, then make a test that
-    // ensures the opacity is being changed on quads in the root RenderPass
-    // when this layer doesn't own a RenderSurfaceImpl.
-    return !m_renderPassesInDrawOrder.isEmpty();
-}
-
 bool DelegatedRendererLayerImpl::hasContributingDelegatedRenderPasses() const
 {
     // The root RenderPass for the layer is merged with its target