Don't create render passes for transparent images.

cc/layer_impl.cc

Index: cc/layer_impl.cc
diff --git a/cc/layer_impl.cc b/cc/layer_impl.cc
index 937b812fdc635e35bac604b2ae975c5f7df8dae5..a60ed25f5e02fb82c48bf7f6a2f129bbc83f4130 100644
--- a/cc/layer_impl.cc
+++ b/cc/layer_impl.cc
@@ -114,15 +114,6 @@ void LayerImpl::createRenderSurface()
     setRenderTarget(this);
 }
 
-bool LayerImpl::descendantDrawsContent()
-{
-    for (size_t i = 0; i < m_children.size(); ++i) {
-        if (m_children[i]->drawsContent() || m_children[i]->descendantDrawsContent())
-            return true;
-    }
-    return false;
-}
-
 scoped_ptr<SharedQuadState> LayerImpl::createSharedQuadState() const
 {
   scoped_ptr<SharedQuadState> state = SharedQuadState::Create();