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 38a40f315cab2288e0fa14718754aad2427e8ec2..535dea78f5834b567623e4c239d160b2eb28a1b5 100644
--- a/cc/layer_tree_impl.cc
+++ b/cc/layer_tree_impl.cc
@@ -92,6 +92,7 @@ void LayerTreeImpl::pushPropertiesTo(LayerTreeImpl* target_tree) {
   target_tree->SetPageScaleDelta(
       target_tree->page_scale_delta() / target_tree->sent_page_scale_delta());
   target_tree->set_sent_page_scale_delta(1);
+  target_tree->SetDeviceViewportSize(device_viewport_size_);
 
   // This should match the property synchronization in
   // LayerTreeHost::finishCommitOnImplThread().
@@ -269,6 +270,18 @@ void LayerTreeImpl::ClearRenderSurfaces() {
   set_needs_update_draw_properties();
 }
 
+void LayerTreeImpl::SetDeviceViewportSize(const gfx::Size& device_viewport_size)
+{
+    if (device_viewport_size_ == device_viewport_size)
+        return;
+
+    device_viewport_size_ = device_viewport_size;
+
+    UpdateMaxScrollOffset();
+
+    layer_tree_host_impl_->OnCanDrawStateChangedForTree(this);
+}
+
 bool LayerTreeImpl::AreVisibleResourcesReady() const {
   TRACE_EVENT0("cc", "LayerTreeImpl::AreVisibleResourcesReady");
 
@@ -428,14 +441,6 @@ float LayerTreeImpl::device_scale_factor() const {
   return layer_tree_host_impl_->deviceScaleFactor();
 }
 
-const gfx::Size& LayerTreeImpl::device_viewport_size() const {
-  return layer_tree_host_impl_->deviceViewportSize();
-}
-
-const gfx::Size& LayerTreeImpl::layout_viewport_size() const {
-  return layer_tree_host_impl_->layoutViewportSize();
-}
-
 std::string LayerTreeImpl::layer_tree_as_text() const {
   return layer_tree_host_impl_->layerTreeAsText();
 }