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

ui/views/animation/ink_drop_host_view.cc

Index: ui/views/animation/ink_drop_host_view.cc
diff --git a/ui/views/animation/ink_drop_host_view.cc b/ui/views/animation/ink_drop_host_view.cc
index e6b1e424155d41e75056cdf1744fc2e7e2684fcc..cf58f1b5443ee544f3741638b1d8230254de03b9 100644
--- a/ui/views/animation/ink_drop_host_view.cc
+++ b/ui/views/animation/ink_drop_host_view.cc
@@ -38,7 +38,8 @@ 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 {
@@ -50,6 +51,8 @@ class InkDropHostView::InkDropGestureHandler : public ui::EventHandler {
 
   ~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();
@@ -223,7 +226,10 @@ bool InkDropHostView::ShouldShowInkDropForFocus() const {
 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());