Fix crash when InkDropHostView::SetHasInkDrop() is called multiple times

ui/views/animation/ink_drop_host_view.cc

 // Copyright 2016 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/views/animation/ink_drop_host_view.h"
 
 #include "ui/events/event.h"
 #include "ui/events/scoped_target_handler.h"
 #include "ui/gfx/color_palette.h"
 #include "ui/gfx/geometry/size_conversions.h"
@@ skipping 21 matching lines @@
 }
 
 }  // namespace
 
 // static
 const int InkDropHostView::kInkDropSmallCornerRadius = 2;
 
 // An EventHandler that is guaranteed to be invoked and is not prone to
 // InkDropHostView descendents who do not call
 // InkDropHostView::OnGestureEvent().
+// Only one instance of this class can exist at any given time. Make sure to
+// delete the old one, if any, *before* instantiating a new one.

[sadrul, 2016/06/26 03:51:31]

You mean only one instance can exist *for a particular host_view*, right?

[mohsen, 2016/06/27 18:59:10]

Right. Updated the comment.

 //
 // TODO(bruthig): Consider getting rid of this class.
 class InkDropHostView::InkDropGestureHandler : public ui::EventHandler {
  public:
   InkDropGestureHandler(InkDropHostView* host_view, InkDrop* ink_drop)
       : target_handler_(new ui::ScopedTargetHandler(host_view, this)),
         host_view_(host_view),
         ink_drop_(ink_drop) {}
 
   ~InkDropGestureHandler() override {}
@@ skipping 162 matching lines @@
 SkColor InkDropHostView::GetInkDropBaseColor() const {
   NOTREACHED();
   return gfx::kPlaceholderColor;
 }
 
 bool InkDropHostView::ShouldShowInkDropForFocus() const {
   return false;
 }
 
 void InkDropHostView::SetHasInkDrop(bool has_an_ink_drop) {
+  gesture_handler_.reset();
   if (has_an_ink_drop) {
     ink_drop_.reset(new InkDropImpl(this));
     gesture_handler_.reset(new InkDropGestureHandler(this, ink_drop_.get()));

[sadrul, 2016/06/26 03:51:31]

Add a comment here that any existing InkDropGestureHandler instance needs to be
destroyed first, before a new instance is created.

But, instead of recreating gesture_handler_, if it's non-null, can you just
change its |ink_drop_|? e.g. InkDropGestureHandler::SetInkDrop(...)

[mohsen, 2016/06/27 18:59:10]

Yes, Added SetInkDrop().

   } else {
-    gesture_handler_.reset();
     ink_drop_.reset(new InkDropStub());
   }
 }
 
 }  // namespace views