Trace main thread commit in flow events.

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index 449d8e4e09a0f614e44ead23cf8677e65fa2dedb..9824d3eea1a7b2e06d6d02c175e8f5f7a2f000d7 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -311,6 +311,14 @@ class CC_EXPORT LayerTreeHost {
 
   size_t num_queued_swap_promises() const { return swap_promise_list_.size(); }
 
+  void trace_commit() {

[Yufeng Shen (Slow to review), 2015/06/16 15:11:05]

Can you use Camel style ? underscore style is usually only for simple
setter/getter. And probably move the implementation to .cc file.

Also a different name more specific to SwapPromise, maybe
OnCommitForSwapPromises()

+    for (unsigned int i = 0; i < num_queued_swap_promises(); i++) {
+      SwapPromise* swap_promise_ = swap_promise_list_.at(i);
+
+      swap_promise_->OnCommit();
+    }

[Yufeng Shen (Slow to review), 2015/06/16 15:11:05]

It can be simplified like this:

for (auto* swap_promise : swap_promise_list_)
    swap_promise->OnCommit()

+  }
+
   void set_surface_id_namespace(uint32_t id_namespace);
   SurfaceSequence CreateSurfaceSequence();