Use message passing for BeginFrameAndCommitState and clean up forced commit logic

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 b969201954863467a622ac7357857c9e1bbaf1bc..12297e7c96dc9d06d53e828c92d3e37ee896f40a 100644
--- a/cc/layer_tree_host.cc
+++ b/cc/layer_tree_host.cc
@@ -500,7 +500,6 @@ bool LayerTreeHost::initializeRendererIfNeeded()
 void LayerTreeHost::updateLayers(ResourceUpdateQueue& queue, size_t memoryAllocationLimitBytes)
 {
     DCHECK(m_rendererInitialized);
-    DCHECK(memoryAllocationLimitBytes);
 
     if (!rootLayer())
         return;
@@ -508,7 +507,8 @@ void LayerTreeHost::updateLayers(ResourceUpdateQueue& queue, size_t memoryAlloca
     if (layoutViewportSize().IsEmpty())
         return;
 
-    m_contentsTextureManager->setMaxMemoryLimitBytes(memoryAllocationLimitBytes);
+    if (memoryAllocationLimitBytes)
+        m_contentsTextureManager->setMaxMemoryLimitBytes(memoryAllocationLimitBytes);
 
     updateLayers(rootLayer(), queue);
 }