Implement a new flow event API that allows binding flow events and regular events.

content/renderer/input/input_handler_proxy.cc

 // Copyright 2013 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 "content/renderer/input/input_handler_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/logging.h"
@@ skipping 200 matching lines @@
 
 InputHandlerProxy::EventDisposition
 InputHandlerProxy::HandleInputEventWithLatencyInfo(
     const WebInputEvent& event,
     ui::LatencyInfo* latency_info) {
   DCHECK(input_handler_);
 
   if (uma_latency_reporting_enabled_)
     ReportInputEventLatencyUma(event, *latency_info);
 
+  TRACE_EVENT_WITH_FLOW0("toplevel", "InputHandlerProxy::HandleInputEventWithLatencyInfo",
+                         TRACE_ID_DONT_MANGLE(latency_info->trace_id),
+                         TRACE_EVENT_FLAG_FLOW_IN | TRACE_EVENT_FLAG_FLOW_OUT);
   TRACE_EVENT_FLOW_STEP0("input,benchmark",
                          "LatencyInfo.Flow",
                          TRACE_ID_DONT_MANGLE(latency_info->trace_id),
                          "HandleInputEventImpl");
 
   scoped_ptr<cc::SwapPromiseMonitor> latency_info_swap_promise_monitor =
       input_handler_->CreateLatencyInfoSwapPromiseMonitor(latency_info);
   InputHandlerProxy::EventDisposition disposition = HandleInputEvent(event);
   return disposition;
 }
@@ skipping 736 matching lines @@
   // trigger a scroll, e.g., with a trivial time delta between fling updates.
   // Return true in this case to prevent early fling termination.
   if (std::abs(clipped_increment.width) < kScrollEpsilon &&
       std::abs(clipped_increment.height) < kScrollEpsilon)
     return true;
 
   return did_scroll;
 }
 
 }  // namespace content