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

cc/layer_tree_host.cc

Index: cc/layer_tree_host.cc
diff --git a/cc/layer_tree_host.cc b/cc/layer_tree_host.cc
index fb99807e60dd968e0146b225061b95c21201ce7e..e5523561d5dc28690a1428c1f0802b27f4e9a79d 100644
--- a/cc/layer_tree_host.cc
+++ b/cc/layer_tree_host.cc
@@ -312,6 +312,7 @@ void LayerTreeHost::finishCommitOnImplThread(LayerTreeHostImpl* hostImpl)
 
     syncTree->SetPageScaleFactorAndLimits(m_pageScaleFactor, m_minPageScaleFactor, m_maxPageScaleFactor);
     syncTree->SetPageScaleDelta(page_scale_delta / sent_page_scale_delta);
+    syncTree->SetViewportSize(layoutViewportSize(), deviceViewportSize());
 
     if (!m_settings.implSidePainting) {
         // If we're not in impl-side painting, the tree is immediately
@@ -319,7 +320,6 @@ void LayerTreeHost::finishCommitOnImplThread(LayerTreeHostImpl* hostImpl)
         syncTree->DidBecomeActive();
     }
 
-    hostImpl->setViewportSize(layoutViewportSize(), deviceViewportSize());
     hostImpl->setDeviceScaleFactor(deviceScaleFactor());
     hostImpl->setDebugState(m_debugState);
     hostImpl->savePaintTime(m_renderingStats.totalPaintTime);