Add impl/comp scrolling instrumentation.

cc/trees/thread_proxy.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/thread_proxy.h"
 
 #include <string>
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
@@ skipping 649 matching lines @@
 
 void ThreadProxy::ScheduledActionSendBeginFrameToMainThread() {
   TRACE_EVENT0("cc", "ThreadProxy::ScheduledActionSendBeginFrameToMainThread");
   scoped_ptr<BeginFrameAndCommitState> begin_frame_state(
       new BeginFrameAndCommitState);
   begin_frame_state->monotonic_frame_begin_time =
       layer_tree_host_impl_->CurrentPhysicalTimeTicks();
   begin_frame_state->scroll_info =
       layer_tree_host_impl_->ProcessScrollDeltas();
 
+  if (!begin_frame_state->scroll_info->scrolls.empty()) {
+    TRACE_EVENT_INSTANT0(
+        "impl-scroll",
+        "ThreadProxy::ScheduledActionSendBeginFrameToMainThread received scroll"
+        " deltas",
+        TRACE_EVENT_SCOPE_THREAD);
+  }
+
   if (!layer_tree_host_impl_->settings().impl_side_painting) {
     DCHECK_GT(layer_tree_host_impl_->memory_allocation_limit_bytes(), 0u);
   }
   begin_frame_state->memory_allocation_limit_bytes =
       layer_tree_host_impl_->memory_allocation_limit_bytes();
   Proxy::MainThreadTaskRunner()->PostTask(
       FROM_HERE,
       base::Bind(&ThreadProxy::BeginFrameOnMainThread,
                  main_thread_weak_ptr_,
                  base::Passed(&begin_frame_state)));
@@ skipping 39 matching lines @@
     TRACE_EVENT0("cc", "EarlyOut_NotVisible");
     bool did_handle = false;
     Proxy::ImplThreadTaskRunner()->PostTask(
         FROM_HERE,
         base::Bind(&ThreadProxy::BeginFrameAbortedByMainThreadOnImplThread,
                    impl_thread_weak_ptr_,
                    did_handle));
     return;
   }
 
-  if (begin_frame_state)
+  if (begin_frame_state) {
+    const bool has_scrolls = !begin_frame_state->scroll_info->scrolls.empty();
+    if (has_scrolls) {
+      // We use async events here because we want to conditionally trace. This
+      // is too spammy otherwise.
+      TRACE_EVENT_ASYNC_BEGIN0(
+          "impl-scroll",
+          "ThreadProxy::BeginFrameOnMainThread",
+          this);
+    }
     layer_tree_host_->ApplyScrollAndScale(*begin_frame_state->scroll_info);
+    if (has_scrolls) {
+      TRACE_EVENT_ASYNC_END0(
+          "impl-scroll",
+          "ThreadProxy::BeginFrameOnMainThread",
+          this);
+    }
+  }
 
   layer_tree_host_->WillBeginFrame();
 
   if (begin_frame_state) {
     layer_tree_host_->UpdateClientAnimations(
         begin_frame_state->monotonic_frame_begin_time);
     layer_tree_host_->AnimateLayers(
         begin_frame_state->monotonic_frame_begin_time);
   }
 
@@ skipping 762 matching lines @@
     DCHECK(layer_tree_host_impl_->settings().impl_side_painting);
     completion_event_for_commit_held_on_tree_activation_->Signal();
     completion_event_for_commit_held_on_tree_activation_ = NULL;
   }
 
   commit_to_activate_duration_history_.InsertSample(
       base::TimeTicks::HighResNow() - commit_complete_time_);
 }
 
 }  // namespace cc