Implement lifetime observer on RenderWidgetHostViewBase.

content/browser/renderer_host/render_widget_host_view_base.cc

 // Copyright (c) 2012 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/browser/renderer_host/render_widget_host_view_base.h"
 
 #include "base/logging.h"
 #include "build/build_config.h"
 #include "content/browser/accessibility/browser_accessibility_manager.h"
 #include "content/browser/gpu/gpu_data_manager_impl.h"
 #include "content/browser/renderer_host/input/synthetic_gesture_target_base.h"
 #include "content/browser/renderer_host/render_process_host_impl.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
+#include "content/browser/renderer_host/render_widget_host_view_base_observer.h"
 #include "content/common/content_switches_internal.h"
 #include "content/public/browser/render_widget_host_view_frame_subscriber.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/geometry/point_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/geometry/size_f.h"
 #include "ui/gfx/screen.h"
 
 #if defined(OS_WIN)
 #include "base/command_line.h"
@@ skipping 346 matching lines @@
     : popup_type_(blink::WebPopupTypeNone),
       background_color_(SK_ColorWHITE),
       mouse_locked_(false),
       showing_context_menu_(false),
       selection_text_offset_(0),
       selection_range_(gfx::Range::InvalidRange()),
       current_device_scale_factor_(0),
       current_display_rotation_(gfx::Display::ROTATE_0),
       pinch_zoom_enabled_(content::IsPinchToZoomEnabled()),
       renderer_frame_number_(0),
-      weak_factory_(this) {
-}
+      weak_factory_(this) {}
 
 RenderWidgetHostViewBase::~RenderWidgetHostViewBase() {
   DCHECK(!mouse_locked_);
+  // We call this here to guarantee that observers are notified before we go
+  // away. However, some subclasses may wish to call this earlier in their
+  // shutdown process, e.g. to force removal from
+  // RenderWidgetHostInputEventRouter's surface map before relinquishing a
+  // host pointer, as in RenderWidgetHostViewGuest. There is no harm in calling
+  // NotifyObserversAboutShutdown() twice, as the observers are required to
+  // de-register on the first call, and so the second call does nothing.

[kenrb, 2016/02/22 17:05:10]

Do you know of any case where this is actually needed?

[wjmaclean, 2016/02/23 13:13:26]

My hope was that, by putting this here, then only sub-classes with special needs
around notifying earlier (e.g. RWHVCF, RWHVG, RWHVMac) would have to make
earlier calls, and all other sub-classes could just default to having it called
here.

+  NotifyObserversAboutShutdown();
+}
+
+void RenderWidgetHostViewBase::NotifyObserversAboutShutdown() {
+  // Note: RenderWidgetHostInputEventRouter is an observer, and uses the
+  // following notification to remove this view from its surface owners map.
+  FOR_EACH_OBSERVER(RenderWidgetHostViewBaseObserver,
+                    observers_,
+                    OnRenderWidgetHostViewBaseDestroyed(this));
+  // All observers are required to disconnect after they are notified.
+  DCHECK(!observers_.might_have_observers());
 }
 
 bool RenderWidgetHostViewBase::OnMessageReceived(const IPC::Message& msg){
   return false;
 }
 
 void RenderWidgetHostViewBase::SetBackgroundColor(SkColor color) {
   background_color_ = color;
 }
 
@@ skipping 299 matching lines @@
       gfx::ToRoundedPoint(point)));
 }
 
 void RenderWidgetHostViewBase::TransformPointToLocalCoordSpace(
     const gfx::Point& point,
     cc::SurfaceId original_surface,
     gfx::Point* transformed_point) {
   *transformed_point = point;
 }
 
+void RenderWidgetHostViewBase::AddObserver(
+    RenderWidgetHostViewBaseObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void RenderWidgetHostViewBase::RemoveObserver(
+    RenderWidgetHostViewBaseObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
 }  // namespace content