Add RAIL tracing category to Chrome tracing.

content/renderer/input/render_widget_input_handler.cc

 // Copyright 2015 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/render_widget_input_handler.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <utility>
 
@@ skipping 225 matching lines @@
   }
 
   ImeEventGuard guard(widget_);
   guard.set_from_ime(from_ime);
 #endif
 
   base::TimeTicks start_time;
   if (base::TimeTicks::IsHighResolution())
     start_time = base::TimeTicks::Now();
 
-  TRACE_EVENT1("renderer,benchmark",
+  TRACE_EVENT1("renderer,benchmark,rail",
                "RenderWidgetInputHandler::OnHandleInputEvent", "event",
                WebInputEventTraits::GetName(input_event.type));
   TRACE_EVENT_SYNTHETIC_DELAY_BEGIN("blink.HandleInputEvent");
   TRACE_EVENT_WITH_FLOW1("input,benchmark", "LatencyInfo.Flow",
                          TRACE_ID_DONT_MANGLE(latency_info.trace_id()),
                          TRACE_EVENT_FLAG_FLOW_IN | TRACE_EVENT_FLAG_FLOW_OUT,
                          "step", "HandleInputEventMain");
 
   // If we don't have a high res timer, these metrics won't be accurate enough
   // to be worth collecting. Note that this does introduce some sampling bias.
@@ skipping 297 matching lines @@
   if (pending_input_event_ack_) {
     TRACE_EVENT_ASYNC_END0("input",
                            "RenderWidgetInputHandler::ThrottledInputEventAck",
                            pending_input_event_ack_.get());
     delegate_->OnInputEventAck(std::move(pending_input_event_ack_));
   }
   total_input_handling_time_this_frame_ = base::TimeDelta();
 }
 
 }  // namespace content