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 7d7678684ab2294f2ff9134796ce331d71e120d9..fa7f287a17120b636a5fdfbb58732fff99ecf703 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)));