Teach input_handler_proxy about once callbacks.

ui/events/blink/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 "ui/events/blink/input_handler_proxy.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 279 matching lines @@
 
 void InputHandlerProxy::WillShutdown() {
   scroll_elasticity_controller_.reset();
   input_handler_ = NULL;
   client_->WillShutdown();
 }
 
 void InputHandlerProxy::HandleInputEventWithLatencyInfo(
     WebScopedInputEvent event,
     const LatencyInfo& latency_info,
-    const EventDispositionCallback& callback) {
+    EventDispositionCallback callback) {
   DCHECK(input_handler_);
 
   if (uma_latency_reporting_enabled_)
     ReportInputEventLatencyUma(*event, latency_info);
 
   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", "HandleInputEventImpl");
 
   std::unique_ptr<EventWithCallback> event_with_callback =
       base::MakeUnique<EventWithCallback>(std::move(event), latency_info,
-                                          tick_clock_->NowTicks(), callback);
+                                          tick_clock_->NowTicks(),
+                                          std::move(callback));
 
   // Note: Other input can race ahead of gesture input as they don't have to go
   // through the queue, but we believe it's OK to do so.
   if (!compositor_event_queue_ ||
       !IsGestureScrollOrFlingOrPinch(event_with_callback->event().GetType())) {
     DispatchSingleInputEvent(std::move(event_with_callback),
                              tick_clock_->NowTicks());
     return;
   }
 
@@ skipping 1320 matching lines @@
                  scroll_elasticity_controller_->GetWeakPtr(), gesture_event,
                  scroll_result));
 }
 
 void InputHandlerProxy::SetTickClockForTesting(
     std::unique_ptr<base::TickClock> tick_clock) {
   tick_clock_ = std::move(tick_clock);
 }
 
 }  // namespace ui