cc: Call PrepareTiles when becoming visible in browser only.

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index b6d120b48053a54c3cfbf34b9646b6db407968f8..5637830883fd8e9766f6ac609a9e7cdd29d13e3c 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -122,7 +122,14 @@ void SingleThreadProxy::SetLayerTreeHostClientReady() {
 void SingleThreadProxy::SetVisible(bool visible) {
   TRACE_EVENT1("cc", "SingleThreadProxy::SetVisible", "visible", visible);
   DebugScopedSetImplThread impl(this);
+
+  bool was_visible = layer_tree_host_impl_->visible();
   layer_tree_host_impl_->SetVisible(visible);
+
+  // Call PrepareTiles in case we're waiting for ready to draw.
+  if (!was_visible && visible)
+    layer_tree_host_impl_->PrepareTiles();
+
   if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->SetVisible(layer_tree_host_impl_->visible());
   // Changing visibility could change ShouldComposite().