cc: Emit fewer trace events for SetNeeds{Animate,UpdateLayers,Commit}

Only emit a trace event for SetNeeds{Animate,UpdateLayers,Commit} if we
actually sent a request to the impl thread. This cuts down a potentially
large number of trace events coming from these functions.
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1290303004

Cr-Commit-Position: refs/heads/master@{#344206}

2 files changed, 18 insertions, 9 deletions

diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index ba1f946..e530931 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -236,7 +236,7 @@ void ThreadProxy::SetRendererCapabilitiesMainThreadCopy(
   main().renderer_capabilities_main_thread_copy = capabilities;
 }
 
-void ThreadProxy::SendCommitRequestToImplThreadIfNeeded(
+bool ThreadProxy::SendCommitRequestToImplThreadIfNeeded(
     CommitPipelineStage required_stage) {
   DCHECK(IsMainThread());
   DCHECK_NE(NO_PIPELINE_STAGE, required_stage);
@@ -245,11 +245,12 @@ void ThreadProxy::SendCommitRequestToImplThreadIfNeeded(
   main().max_requested_pipeline_stage =
       std::max(main().max_requested_pipeline_stage, required_stage);
   if (already_posted)
-    return;
+    return false;
   Proxy::ImplThreadTaskRunner()->PostTask(
       FROM_HERE,
       base::Bind(&ThreadProxy::SetNeedsCommitOnImplThread,
                  impl_thread_weak_ptr_));
+  return true;
 }
 
 void ThreadProxy::DidCompletePageScaleAnimation() {
@@ -265,20 +266,24 @@ const RendererCapabilities& ThreadProxy::GetRendererCapabilities() const {
 
 void ThreadProxy::SetNeedsAnimate() {
   DCHECK(IsMainThread());
-  TRACE_EVENT0("cc", "ThreadProxy::SetNeedsAnimate");
-  SendCommitRequestToImplThreadIfNeeded(ANIMATE_PIPELINE_STAGE);
+  if (SendCommitRequestToImplThreadIfNeeded(ANIMATE_PIPELINE_STAGE)) {
+    TRACE_EVENT_INSTANT0("cc", "ThreadProxy::SetNeedsAnimate",
+                         TRACE_EVENT_SCOPE_THREAD);
+  }
 }
 
 void ThreadProxy::SetNeedsUpdateLayers() {
   DCHECK(IsMainThread());
-  TRACE_EVENT0("cc", "ThreadProxy::SetNeedsUpdateLayers");
   // If we are currently animating, make sure we also update the layers.
   if (main().current_pipeline_stage == ANIMATE_PIPELINE_STAGE) {
     main().final_pipeline_stage =
         std::max(main().final_pipeline_stage, UPDATE_LAYERS_PIPELINE_STAGE);
     return;
   }
-  SendCommitRequestToImplThreadIfNeeded(UPDATE_LAYERS_PIPELINE_STAGE);
+  if (SendCommitRequestToImplThreadIfNeeded(UPDATE_LAYERS_PIPELINE_STAGE)) {
+    TRACE_EVENT_INSTANT0("cc", "ThreadProxy::SetNeedsUpdateLayers",
+                         TRACE_EVENT_SCOPE_THREAD);
+  }
 }
 
 void ThreadProxy::SetNeedsCommit() {
@@ -291,8 +296,10 @@ void ThreadProxy::SetNeedsCommit() {
         std::max(main().final_pipeline_stage, COMMIT_PIPELINE_STAGE);
     return;
   }
-  TRACE_EVENT0("cc", "ThreadProxy::SetNeedsCommit");
-  SendCommitRequestToImplThreadIfNeeded(COMMIT_PIPELINE_STAGE);
+  if (SendCommitRequestToImplThreadIfNeeded(COMMIT_PIPELINE_STAGE)) {
+    TRACE_EVENT_INSTANT0("cc", "ThreadProxy::SetNeedsCommit",
+                         TRACE_EVENT_SCOPE_THREAD);
+  }
 }
 
 void ThreadProxy::UpdateRendererCapabilitiesOnImplThread() {
diff --git a/cc/trees/thread_proxy.h b/cc/trees/thread_proxy.h
index a2e7bec..ae9c733 100644
--- a/cc/trees/thread_proxy.h
+++ b/cc/trees/thread_proxy.h
@@ -255,7 +255,9 @@ class CC_EXPORT ThreadProxy : public Proxy,
   void RequestNewOutputSurface();
   void DidInitializeOutputSurface(bool success,
                                   const RendererCapabilities& capabilities);
-  void SendCommitRequestToImplThreadIfNeeded(
+  // Returns |true| if the request was actually sent, |false| if one was
+  // already outstanding.
+  bool SendCommitRequestToImplThreadIfNeeded(
       CommitPipelineStage required_stage);
   void DidCompletePageScaleAnimation();