cc: Only allow trees created at the current viewport size to draw.

cc/layer_tree_impl.cc

Index: cc/layer_tree_impl.cc
diff --git a/cc/layer_tree_impl.cc b/cc/layer_tree_impl.cc
index 832ecaa84d1da7fe6abe6172d483d6215d2b4d67..b0d071efd64d7bf84ccca61ad9c15dd0fc246474 100644
--- a/cc/layer_tree_impl.cc
+++ b/cc/layer_tree_impl.cc
@@ -27,6 +27,7 @@ LayerTreeImpl::LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl)
       max_page_scale_factor_(0),
       scrolling_layer_id_from_previous_tree_(0),
       contents_textures_purged_(false),
+      viewport_size_invalid_(false),
       needs_update_draw_properties_(true),
       needs_full_tree_sync_(true) {
 }
@@ -104,6 +105,11 @@ void LayerTreeImpl::pushPropertiesTo(LayerTreeImpl* target_tree) {
   else
     target_tree->ResetContentsTexturesPurged();
 
+  if (ViewportSizeInvalid())
+    target_tree->SetViewportSizeInvalid();
+  else
+    target_tree->ResetViewportSizeInvalid();
+
   if (hud_layer())
     target_tree->set_hud_layer(static_cast<HeadsUpDisplayLayerImpl*>(
         LayerTreeHostCommon::findLayerInSubtree(
@@ -346,6 +352,20 @@ void LayerTreeImpl::ResetContentsTexturesPurged() {
   layer_tree_host_impl_->OnCanDrawStateChangedForTree(this);
 }
 
+bool LayerTreeImpl::ViewportSizeInvalid() const {
+  return viewport_size_invalid_;
+}
+
+void LayerTreeImpl::SetViewportSizeInvalid() {
+  viewport_size_invalid_ = true;
+  layer_tree_host_impl_->OnCanDrawStateChangedForTree(this);
+}
+
+void LayerTreeImpl::ResetViewportSizeInvalid() {
+  viewport_size_invalid_ = false;
+  layer_tree_host_impl_->OnCanDrawStateChangedForTree(this);
+}
+
 Proxy* LayerTreeImpl::proxy() const {
   return layer_tree_host_impl_->proxy();
 }