Fix crash which occurs when a widget destroys itself as a result of ET_GESTURE_TAP_DOWN

ui/views/widget/root_view.cc

Index: ui/views/widget/root_view.cc
diff --git a/ui/views/widget/root_view.cc b/ui/views/widget/root_view.cc
index f3ad2a08d6849b779e7bf5634218b57b6144176f..78bba831ddbee5ad4777f7cda976770c974468c4 100644
--- a/ui/views/widget/root_view.cc
+++ b/ui/views/widget/root_view.cc
@@ -19,7 +19,6 @@
 #include "ui/views/views_switches.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/widget/widget_delegate.h"
-#include "ui/views/widget/widget_deletion_observer.h"
 
 #if defined(USE_AURA)
 #include "ui/base/cursor/cursor.h"
@@ -224,7 +223,10 @@ void RootView::DispatchGestureEvent(ui::GestureEvent* event) {
         (event->IsScrollGestureEvent() || event->IsFlingScrollEvent())  ?
             scroll_gesture_handler_ : gesture_handler_;
     ui::GestureEvent handler_event(*event, static_cast<View*>(this), handler);
-    DispatchEventToTarget(handler, &handler_event);
+    ui::EventDispatchDetails dispatch_details =
+        DispatchEventToTarget(handler, &handler_event);
+    if (dispatch_details.dispatcher_destroyed)
+      return;
 
     if (event->type() == ui::ET_GESTURE_END &&
         event->details().touch_points() <= 1) {
@@ -312,7 +314,10 @@ void RootView::DispatchGestureEvent(ui::GestureEvent* event) {
     // See if this view wants to handle the Gesture.
     ui::GestureEvent gesture_event(*event, static_cast<View*>(this),
                                    gesture_handler_);
-    DispatchEventToTarget(gesture_handler_, &gesture_event);
+    ui::EventDispatchDetails dispatch_details =
+        DispatchEventToTarget(gesture_handler_, &gesture_event);
+    if (dispatch_details.dispatcher_destroyed)
+      return;
 
     // The view could have removed itself from the tree when handling
     // OnGestureEvent(). So handle as per OnMousePressed. NB: we
@@ -447,12 +452,10 @@ bool RootView::OnMousePressed(const ui::MouseEvent& event) {
       mouse_pressed_event.set_flags(event.flags() & ~ui::EF_IS_DOUBLE_CLICK);
 
     drag_info_.Reset();
-    {
-      WidgetDeletionObserver widget_deletion_observer(widget_);
-      DispatchEventToTarget(mouse_pressed_handler_, &mouse_pressed_event);
-      if (!widget_deletion_observer.IsWidgetAlive())
-        return mouse_pressed_event.handled();
-    }
+    ui::EventDispatchDetails dispatch_details =
+        DispatchEventToTarget(mouse_pressed_handler_, &mouse_pressed_event);
+    if (dispatch_details.dispatcher_destroyed)
+      return mouse_pressed_event.handled();
 
     // The view could have removed itself from the tree when handling
     // OnMousePressed().  In this case, the removal notification will have
@@ -702,12 +705,14 @@ void RootView::SetMouseLocationAndFlags(const ui::MouseEvent& event) {
   last_mouse_event_y_ = event.y();
 }
 
-void RootView::DispatchEventToTarget(View* target, ui::Event* event) {
+ui::EventDispatchDetails RootView::DispatchEventToTarget(View* target,
+                                                         ui::Event* event) {
   View* old_target = event_dispatch_target_;
   event_dispatch_target_ = target;
   ui::EventDispatchDetails details = DispatchEvent(target, event);
   if (!details.dispatcher_destroyed)
     event_dispatch_target_ = old_target;
+  return details;
 }
 
 void RootView::NotifyEnterExitOfDescendant(const ui::MouseEvent& event,