Refactoring to make adding ink drop animations easier

ui/events/scoped_target_handler.cc

Index: ui/events/scoped_target_handler.cc
diff --git a/ui/events/scoped_target_handler.cc b/ui/events/scoped_target_handler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..62439cb82fb7e35bf9d1dfcc3442b565c53b66f6
--- /dev/null
+++ b/ui/events/scoped_target_handler.cc
@@ -0,0 +1,23 @@
+// Copyright 2015 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/events/scoped_target_handler.h"
+
+#include "ui/events/event.h"
+#include "ui/events/event_target.h"
+
+namespace ui {
+
+ScopedTargetHandler::ScopedTargetHandler(EventTarget* target,
+                                         EventHandler* handler)
+    : target_(target), handler_(handler) {
+  original_handler_ = target_->SetTargetHandler(handler);
+}
+
+ScopedTargetHandler::~ScopedTargetHandler() {
+  EventHandler* handler = target_->SetTargetHandler(original_handler_);
+  DCHECK_EQ(handler_, handler);
+}
+
+}  // namespace ui