Refined DCHECK preventing multiple event forwarders in VA tree path

ui/android/view_android.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/android/view_android.h"
 
 #include <algorithm>
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_string.h"
@@ skipping 97 matching lines @@
         << "Root of the ViewAndroid can have at most one handler.";
     event_forwarder_.reset(new EventForwarder(this));
   }
   return event_forwarder_->GetJavaObject();
 }
 
 void ViewAndroid::AddChild(ViewAndroid* child) {
   DCHECK(child);
   DCHECK(std::find(children_.begin(), children_.end(), child) ==
          children_.end());
-  DCHECK(!SubtreeHasEventForwarder(child) || !ViewTreeHasEventForwarder(this))
+  DCHECK(GetWindowAndroid() == this || !SubtreeHasEventForwarder(child) ||
+         !ViewTreeHasEventForwarder(this))

[boliu, 2017/05/08 16:54:55]

the previous check is too strict. check should be there's at most one forwarder
from node to root path, but previous code is checking there's only one forwarder
in the entire tree

but I have no idea what this new check does now

[Jinsuk Kim, 2017/05/10 01:42:10]

Updated the DCHECK to do what's actually intended.

       << "Only one event handler is allowed.";
 
   // The new child goes to the top, which is the end of the list.
   children_.push_back(child);
   if (child->parent_)
     child->RemoveFromParent();
   child->parent_ = this;
 }
 
 // static
@@ skipping 203 matching lines @@
         matched = bound.Contains(e->GetX(0), e->GetY(0));
       }
       if (matched && child->HitTest(send_to_client, *e))
         return true;
     }
   }
   return false;
 }
 
 }  // namespace ui