mus: Introduce API for embedder to dispatch event to the embeded client.

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 173 matching lines @@
       handling_event_overscroll_(nullptr),
       handling_event_type_(WebInputEvent::Undefined),
       context_menu_source_type_(ui::MENU_SOURCE_MOUSE),
       suppress_next_char_events_(false),
       ignore_ack_for_mouse_move_from_debugger_(false) {
   DCHECK(delegate);
   DCHECK(widget);
   delegate->SetInputHandler(this);
 }
 
-RenderWidgetInputHandler::~RenderWidgetInputHandler() {}
+RenderWidgetInputHandler::~RenderWidgetInputHandler() {
+  delegate_->SetInputHandler(nullptr);
+}
 
 void RenderWidgetInputHandler::HandleInputEvent(
     const WebInputEvent& input_event,
     const ui::LatencyInfo& latency_info,
     InputEventDispatchType dispatch_type) {
   base::AutoReset<bool> handling_input_event_resetter(&handling_input_event_,
                                                       true);
   base::AutoReset<WebInputEvent::Type> handling_event_type_resetter(
       &handling_event_type_, input_event.type);
 
@@ skipping 350 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