Move page scale ownership to LayerTreeImpl.

cc/thread_proxy.cc

Index: cc/thread_proxy.cc
diff --git a/cc/thread_proxy.cc b/cc/thread_proxy.cc
index dc50fc15c9e1f8e419b3d35f1f01c5e9d3bbc8be..2d24429e118bbe0978c7fbdea8a9d9dc1d54324b 100644
--- a/cc/thread_proxy.cc
+++ b/cc/thread_proxy.cc
@@ -564,7 +564,7 @@ void ThreadProxy::scheduledActionBeginFrame()
     scoped_ptr<BeginFrameAndCommitState> beginFrameState(new BeginFrameAndCommitState);
     beginFrameState->monotonicFrameBeginTime = base::TimeTicks::Now();
     beginFrameState->scrollInfo = m_layerTreeHostImpl->processScrollDeltas();
-    beginFrameState->implTransform = m_layerTreeHostImpl->implTransform();
+    beginFrameState->implTransform = m_layerTreeHostImpl->activeTree()->ImplTransform();
     DCHECK_GT(m_layerTreeHostImpl->memoryAllocationLimitBytes(), 0u);
     beginFrameState->memoryAllocationLimitBytes = m_layerTreeHostImpl->memoryAllocationLimitBytes();
     Proxy::mainThread()->postTask(base::Bind(&ThreadProxy::beginFrame, m_mainThreadWeakPtr, base::Passed(&beginFrameState)));