Returning early when setting a frame name to the same name.

third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 1038 matching lines @@
         return nullAtom;
 
     return frame()->tree().name();
 }
 
 void LocalDOMWindow::setName(const AtomicString& name)
 {
     if (!isCurrentlyDisplayedInFrame())
         return;
 
+    if (name == frame()->tree().name())
+        return;

[Łukasz Anforowicz, 2016/06/10 00:06:57]

Alex rightfully suggested that we should also short-circuit here (to avoid
unnecessary IPC to the browser).

Note that even with the early return above, we still need to tweak
FrameTree::setName, because it has more callers than just
LocalDOMWindow::setName.

+
     frame()->tree().setName(name);
     ASSERT(frame()->loader().client());
     frame()->loader().client()->didChangeName(name, frame()->tree().uniqueName());
 }
 
 void LocalDOMWindow::setStatus(const String& string)
 {
     m_status = string;
 
     if (!frame())
@@ skipping 481 matching lines @@
 {
     // If the LocalDOMWindow still has a frame reference, that frame must point
     // back to this LocalDOMWindow: otherwise, it's easy to get into a situation
     // where script execution leaks between different LocalDOMWindows.
     if (m_frameObserver->frame())
         ASSERT_WITH_SECURITY_IMPLICATION(m_frameObserver->frame()->domWindow() == this);
     return m_frameObserver->frame();
 }
 
 } // namespace blink