Adding a way to associate Android Activities with PlatformWindowAndroid

ui/aura/window_tree_host_platform.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 "ui/aura/window_tree_host_platform.h"
 
 #include "base/trace_event/trace_event.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/compositor/compositor.h"
 #include "ui/events/event.h"
 #include "ui/gfx/screen.h"
 
 #if defined(OS_ANDROID)
+#include "ui/aura/client/aura_constants.h"
 #include "ui/platform_window/android/platform_window_android.h"
 #endif
 
 #if defined(USE_OZONE)
 #include "ui/ozone/public/ozone_platform.h"
 #endif
 
 #if defined(OS_WIN)
 #include "base/message_loop/message_loop.h"
 #include "ui/base/cursor/cursor_loader_win.h"
@@ skipping 40 matching lines @@
 
 ui::EventSource* WindowTreeHostPlatform::GetEventSource() {
   return this;
 }
 
 gfx::AcceleratedWidget WindowTreeHostPlatform::GetAcceleratedWidget() {
   return widget_;
 }
 
 void WindowTreeHostPlatform::ShowImpl() {
+#if defined(OS_ANDROID)
+  ui::PlatformWindowAndroid* pwa =
+      ui::PlatformWindowAndroid::From(window_.get());
+  if (!pwa->IsAttachedToActivity()) {
+    jobject activity = window()->GetProperty(
+        aura::client::kActivityForRootWindow);
+    pwa->AttachToActivity(activity);
+  }
+#endif
   window_->Show();
 }
 
 void WindowTreeHostPlatform::HideImpl() {
   window_->Hide();
 }
 
 gfx::Rect WindowTreeHostPlatform::GetBounds() const {
   return window_->GetBounds();
 }
@@ skipping 99 matching lines @@
   DCHECK_EQ(widget, widget_);
   widget_ = gfx::kNullAcceleratedWidget;
 }
 
 void WindowTreeHostPlatform::OnActivationChanged(bool active) {
   if (active)
     OnHostActivated();
 }
 
 }  // namespace aura