Wire up Android back button in SkyShell

sky/engine/public/sky/sky_view.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 "config.h"
 #include "sky/engine/public/sky/sky_view.h"
 
 #include "base/bind.h"
 #include "base/trace_event/trace_event.h"
 #include "sky/engine/core/events/GestureEvent.h"
@@ skipping 73 matching lines @@
       data_->view_->handleInputEvent(PointerEvent::create(event));
   } else if (WebInputEvent::isGestureEventType(inputEvent.type)) {
       const WebGestureEvent& event = static_cast<const WebGestureEvent&>(inputEvent);
       data_->view_->handleInputEvent(GestureEvent::create(event));
   } else if (WebInputEvent::isKeyboardEventType(inputEvent.type)) {
       const WebKeyboardEvent& event = static_cast<const WebKeyboardEvent&>(inputEvent);
       data_->view_->handleInputEvent(KeyboardEvent::create(event));
   } else if (WebInputEvent::isWheelEventType(inputEvent.type)) {
       const WebWheelEvent& event = static_cast<const WebWheelEvent&>(inputEvent);
       data_->view_->handleInputEvent(WheelEvent::create(event));
+  } else if (inputEvent.type == WebInputEvent::Back) {
+      data_->view_->handleInputEvent(Event::create("back"));
   }
 
 }
 
 void SkyView::ScheduleFrame() {
   client_->ScheduleFrame();
 }
 
 } // namespace blink