Use WeakPtr to RenderWidgetHostViewBase in InputEventRouter.

content/browser/renderer_host/render_widget_host_input_event_router.cc

Index: content/browser/renderer_host/render_widget_host_input_event_router.cc
diff --git a/content/browser/renderer_host/render_widget_host_input_event_router.cc b/content/browser/renderer_host/render_widget_host_input_event_router.cc
index 449b2f6850247e2b6f54da5d8ea38b04b60b73c7..d6059944d669068b6628788cd3b1a837ea2fdb0c 100644
--- a/content/browser/renderer_host/render_widget_host_input_event_router.cc
+++ b/content/browser/renderer_host/render_widget_host_input_event_router.cc
@@ -11,13 +11,14 @@
 namespace content {
 
 RenderWidgetHostInputEventRouter::RenderWidgetHostInputEventRouter()
-    : current_touch_target_(nullptr), active_touches_(0) {}
+    : has_current_touch_target_(false), active_touches_(0) {}
 
 RenderWidgetHostInputEventRouter::~RenderWidgetHostInputEventRouter() {
   owner_map_.clear();
 }
 
-RenderWidgetHostViewBase* RenderWidgetHostInputEventRouter::FindEventTarget(
+RenderWidgetHostInputEventRouter::WeakTarget

[nasko, 2015/12/22 18:16:33]

Why does this method need to return the WeakTarget type? Can't it return a the
pointer type, since it needs to be checked by the callers anyway.

[wjmaclean, 2015/12/22 18:39:55]

It doesn't have to return the WeakPtr ... I'll change this.

+RenderWidgetHostInputEventRouter::FindEventTarget(
     RenderWidgetHostViewBase* root_view,
     const gfx::Point& point,
     gfx::Point* transformed_point) {
@@ -25,7 +26,7 @@ RenderWidgetHostViewBase* RenderWidgetHostInputEventRouter::FindEventTarget(
   // hit testing.
   if (owner_map_.size() <= 1) {
     *transformed_point = point;
-    return root_view;
+    return root_view->GetWeakPtr();
   }
 
   // The conversion of point to transform_point is done over the course of the
@@ -40,7 +41,7 @@ RenderWidgetHostViewBase* RenderWidgetHostInputEventRouter::FindEventTarget(
   // it likely means the RenderWidgetHostView has been destroyed but its
   // parent frame has not sent a new compositor frame since that happened.
   if (iter == owner_map_.end())
-    return root_view;
+    return root_view->GetWeakPtr();
   return iter->second;
 }
 
@@ -48,24 +49,26 @@ void RenderWidgetHostInputEventRouter::RouteMouseEvent(
     RenderWidgetHostViewBase* root_view,
     blink::WebMouseEvent* event) {
   gfx::Point transformed_point;
-  RenderWidgetHostViewBase* target = FindEventTarget(
-      root_view, gfx::Point(event->x, event->y), &transformed_point);
+  WeakTarget target = FindEventTarget(root_view, gfx::Point(event->x, event->y),
+                                      &transformed_point);
   event->x = transformed_point.x();
   event->y = transformed_point.y();
 
-  target->ProcessMouseEvent(*event);
+  if (target)

[nasko, 2015/12/22 18:16:33]

Let'd use early returns - if (!target) return, right after the actual call to
FindEventTarget.

[wjmaclean, 2015/12/22 18:39:55]

Done.

+    target->ProcessMouseEvent(*event);
 }
 
 void RenderWidgetHostInputEventRouter::RouteMouseWheelEvent(
     RenderWidgetHostViewBase* root_view,
     blink::WebMouseWheelEvent* event) {
   gfx::Point transformed_point;
-  RenderWidgetHostViewBase* target = FindEventTarget(
-      root_view, gfx::Point(event->x, event->y), &transformed_point);
+  WeakTarget target = FindEventTarget(root_view, gfx::Point(event->x, event->y),
+                                      &transformed_point);
   event->x = transformed_point.x();
   event->y = transformed_point.y();
 
-  target->ProcessMouseWheelEvent(*event);
+  if (target)

[nasko, 2015/12/22 18:16:33]

Same as above, early return.

[wjmaclean, 2015/12/22 18:39:55]

Done.

+    target->ProcessMouseWheelEvent(*event);
 }
 
 void RenderWidgetHostInputEventRouter::RouteTouchEvent(
@@ -83,23 +86,29 @@ void RenderWidgetHostInputEventRouter::RouteTouchEvent(
                                   event->touches[0].position.y);
         current_touch_target_ =
             FindEventTarget(root_view, original_point, &transformed_point);

[nasko, 2015/12/22 18:16:33]

You could just call ->GetWeakPtr() here, since it is the only place you really
need a weak pointer.

[wjmaclean, 2015/12/22 18:39:55]

I don't understand? You mean call it on current_touch_target? or root_view?

The former could be stale (we'll only know if we store the WeakPtr in the map).
The latter is always a value provided by the caller, so we trust it not to be
stale.

+        has_current_touch_target_ = true;

[Fady Samuel, 2015/12/22 18:06:43]

Is this flag necessary? It seems you only use it for DCHECKing?

       }
       ++active_touches_;
-      current_touch_target_->ProcessTouchEvent(*event, latency);
+      if (current_touch_target_.get())
+        current_touch_target_->ProcessTouchEvent(*event, latency);
       break;
     }
     case blink::WebInputEvent::TouchMove:
-      DCHECK(current_touch_target_);
-      current_touch_target_->ProcessTouchEvent(*event, latency);
+      DCHECK(has_current_touch_target_);
+      if (current_touch_target_.get())
+        current_touch_target_->ProcessTouchEvent(*event, latency);
       break;
     case blink::WebInputEvent::TouchEnd:
     case blink::WebInputEvent::TouchCancel:
       DCHECK(active_touches_);
-      DCHECK(current_touch_target_);
-      current_touch_target_->ProcessTouchEvent(*event, latency);
+      DCHECK(has_current_touch_target_);
+      if (current_touch_target_.get())
+        current_touch_target_->ProcessTouchEvent(*event, latency);
       --active_touches_;
-      if (!active_touches_)
-        current_touch_target_ = nullptr;
+      if (!active_touches_) {
+        current_touch_target_ = WeakTarget();
+        has_current_touch_target_ = false;
+      }
       break;
     default:
       NOTREACHED();
@@ -110,7 +119,7 @@ void RenderWidgetHostInputEventRouter::AddSurfaceIdNamespaceOwner(
     uint32_t id,
     RenderWidgetHostViewBase* owner) {
   DCHECK(owner_map_.find(id) == owner_map_.end());
-  owner_map_.insert(std::make_pair(id, owner));
+  owner_map_.insert(std::make_pair(id, owner->GetWeakPtr()));
 }
 
 void RenderWidgetHostInputEventRouter::RemoveSurfaceIdNamespaceOwner(