Implement scroll handler latency tracking

cc/trees/layer_tree_host.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/layer_tree_host.h"
 
 #include <algorithm>
 #include <stack>
 #include <string>
 
 #include "base/atomic_sequence_num.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "cc/animation/animation_registrar.h"
 #include "cc/animation/layer_animation_controller.h"
+#include "cc/base/latency_info_swap_promise.h"
 #include "cc/base/math_util.h"
 #include "cc/debug/devtools_instrumentation.h"
 #include "cc/debug/rendering_stats_instrumentation.h"
 #include "cc/input/layer_selection_bound.h"
 #include "cc/input/top_controls_manager.h"
 #include "cc/layers/heads_up_display_layer.h"
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_iterator.h"
 #include "cc/layers/painted_scrollbar_layer.h"
@@ skipping 983 matching lines @@
     occlusion_tracker.LeaveLayer(it);
   }
 
   in_paint_layer_contents_ = false;
 }
 
 void LayerTreeHost::ApplyScrollAndScale(const ScrollAndScaleSet& info) {
   if (!root_layer_.get())
     return;
 
+  for (size_t i = 0; i < info.latency_infos.size(); ++i) {
+    ui::LatencyInfo latency_info = info.latency_infos[i];
+    TRACE_EVENT_FLOW_STEP0("input",
+                           "LatencyInfo.Flow",
+                           TRACE_ID_DONT_MANGLE(latency_info.trace_id),
+                           "Blink scroll update");

[danakj, 2014/07/08 16:49:07]

layering violation: cc doesn't know about blink. You can say main-thread scroll
update or something like that

[Sami, 2014/07/09 13:28:55]

Ah, sorry for the slip-up :) Fixed.

+    scoped_ptr<SwapPromise> swap_promise(
+        new LatencyInfoSwapPromise(latency_info));
+    QueueSwapPromise(swap_promise.Pass());
+  }
+
   gfx::Vector2d inner_viewport_scroll_delta;
   gfx::Vector2d outer_viewport_scroll_delta;
 
   for (size_t i = 0; i < info.scrolls.size(); ++i) {
     Layer* layer =
         LayerTreeHostCommon::FindLayerInSubtree(root_layer_.get(),
                                                 info.scrolls[i].layer_id);
     if (!layer)
       continue;
     if (layer == outer_viewport_scroll_layer_.get()) {
@@ skipping 238 matching lines @@
   swap_promise_list_.push_back(swap_promise.Pass());
 }
 
 void LayerTreeHost::BreakSwapPromises(SwapPromise::DidNotSwapReason reason) {
   for (size_t i = 0; i < swap_promise_list_.size(); i++)
     swap_promise_list_[i]->DidNotSwap(reason);
   swap_promise_list_.clear();
 }
 
 }  // namespace cc