Refined DCHECK preventing multiple event forwarders in VA tree path

ui/android/view_android.h

 // Copyright 2013 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.
 
 #ifndef UI_ANDROID_VIEW_ANDROID_H_
 #define UI_ANDROID_VIEW_ANDROID_H_
 
 #include <list>
 
 #include "base/android/jni_weak_ref.h"
@@ skipping 160 matching lines @@
   static bool SendTouchEventToClient(bool for_touch_handle,
                                      ViewClient* client,
                                      const MotionEventAndroid& event);
   static bool SendMouseEventToClient(ViewClient* client,
                                      const MotionEventAndroid& event);
   static bool SendMouseWheelEventToClient(ViewClient* client,
                                           const MotionEventAndroid& event);
 
   bool has_event_forwarder() const { return !!event_forwarder_; }
 
-  // Returns true if any node of the tree along the hierarchy (view's children
-  // and parents) already has |EventForwarder| attached to it.
-  static bool ViewTreeHasEventForwarder(ViewAndroid* view);
-
-  // Returns true if any children node (or self) has |EventForwarder|.
-  static bool SubtreeHasEventForwarder(ViewAndroid* view);
+  // Checks if there is any path from leaf to top that has more than one event
+  // forwarder if |tree| is added to |node| as a child. |has_forwarder| is true
+  // if |node| has (or will have) an event forwarder.
+  static bool HasMultipleEventForwarder(ViewAndroid* node,
+                                        bool has_forwarder,
+                                        ViewAndroid* tree);
+  static bool HasMultipleEventForwarderInAnyPath(ViewAndroid* node,
+                                                 bool forwarder_found);
 
   // Returns the Java delegate for this view. This is used to delegate work
   // up to the embedding view (or the embedder that can deal with the
   // implementation details).
   const base::android::ScopedJavaLocalRef<jobject>
       GetViewAndroidDelegate() const;
 
   std::list<ViewAndroid*> children_;
   scoped_refptr<cc::Layer> layer_;
   JavaObjectWeakGlobalRef delegate_;
 
   ViewClient* const client_;
 
   // Basic view layout information. Used to do hit testing deciding whether
   // the passed events should be processed by the view.
   LayoutParams layout_params_;
 
   gfx::Vector2dF content_offset_;  // in CSS pixel.
   std::unique_ptr<EventForwarder> event_forwarder_;
 
   DISALLOW_COPY_AND_ASSIGN(ViewAndroid);
 };
 
 }  // namespace ui
 
 #endif  // UI_ANDROID_VIEW_ANDROID_H_