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

cc/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
@@ skipping 216 matching lines @@
     // in the proper places and update the notifyIfCanDrawChanged test.
 
     if (!rootLayer()) {
         TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw no root layer");
         return false;
     }
     if (deviceViewportSize().IsEmpty()) {
         TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw empty viewport");
         return false;
     }
+    if (m_activeTree->ViewportSizeInvalid()) {
+        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw viewport size recently changed");
+        return false;
+    }
     if (!m_renderer) {
         TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw no renderer");
         return false;
     }
     if (m_activeTree->ContentsTexturesPurged()) {
         TRACE_EVENT_INSTANT0("cc", "LayerTreeHostImpl::canDraw contents textures purged");
         return false;
     }
     return true;
 }
@@ skipping 848 matching lines @@
         pendingTree()->set_needs_update_draw_properties();
 
     return true;
 }
 
 void LayerTreeHostImpl::setViewportSize(const gfx::Size& layoutViewportSize, const gfx::Size& deviceViewportSize)
 {
     if (layoutViewportSize == m_layoutViewportSize && deviceViewportSize == m_deviceViewportSize)
         return;
 
+    if (pendingTree() && m_deviceViewportSize != deviceViewportSize)
+        activeTree()->SetViewportSizeInvalid();
+
     m_layoutViewportSize = layoutViewportSize;
     m_deviceViewportSize = deviceViewportSize;
 
     updateMaxScrollOffset();
 
     if (m_renderer)
         m_renderer->viewportChanged();
 
     m_client->onCanDrawStateChanged(canDraw());
 }
@@ skipping 650 matching lines @@
     if (m_tileManager)
         m_tileManager->SetRecordRenderingStats(m_debugState.recordRenderingStats());
 }
 
 void LayerTreeHostImpl::savePaintTime(const base::TimeDelta& totalPaintTime)
 {
     m_paintTimeCounter->SavePaintTime(totalPaintTime);
 }
 
 }  // namespace cc