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 20 matching lines @@
   return gfx::ScaleToCeiledSize(gfx::Size(small_size), kLargeInkDropScale);
 }
 
 }  // 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().
+// InkDropHostView::OnGestureEvent().  Only one instance of this class can exist
+// at any given time for each ink drop host view.
 //
 // 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 {}
 
+  void SetInkDrop(InkDrop* ink_drop) { ink_drop_ = ink_drop; }
+
   // ui::EventHandler:
   void OnGestureEvent(ui::GestureEvent* event) override {
     InkDropState current_ink_drop_state = ink_drop_->GetTargetInkDropState();
 
     InkDropState ink_drop_state = InkDropState::HIDDEN;
     switch (event->type()) {
       case ui::ET_GESTURE_TAP_DOWN:
         ink_drop_state = InkDropState::ACTION_PENDING;
         // The ui::ET_GESTURE_TAP_DOWN event needs to be marked as handled so
         // that
@@ skipping 153 matching lines @@
   return gfx::kPlaceholderColor;
 }
 
 bool InkDropHostView::ShouldShowInkDropForFocus() const {
   return false;
 }
 
 void InkDropHostView::SetHasInkDrop(bool has_an_ink_drop) {
   if (has_an_ink_drop) {
     ink_drop_.reset(new InkDropImpl(this));
-    gesture_handler_.reset(new InkDropGestureHandler(this, ink_drop_.get()));
+    if (!gesture_handler_)
+      gesture_handler_.reset(new InkDropGestureHandler(this, ink_drop_.get()));
+    else
+      gesture_handler_->SetInkDrop(ink_drop_.get());
   } else {
     gesture_handler_.reset();
     ink_drop_.reset(new InkDropStub());
   }
 }
 
 }  // namespace views