Early out if the scroll position passed in by js is NaN

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 1385 matching lines @@
 {
     if (!isCurrentlyDisplayedInFrame())
         return;
 
     document()->updateLayoutIgnorePendingStylesheets();
 
     RefPtrWillBeRawPtr<FrameView> view = m_frame->view();
     if (!view)
         return;
 
+    // If the scrollTo position x/y is NaN, explicitly set it to 0.
+    if (x != x)

[Rick Byers, 2014/10/21 20:44:15]

use std::isnan (then you can also remove the comment which will be redundant
with the code).

+        x = 0;
+    if (y != y)
+        y = 0;
+
     DoublePoint layoutPos(x * m_frame->pageZoomFactor(), y * m_frame->pageZoomFactor());
     view->setScrollPosition(layoutPos, scrollBehavior);
 }
 
 void LocalDOMWindow::scrollTo(double x, double y, const ScrollOptions& scrollOptions, ExceptionState& exceptionState) const
 {
     ScrollBehavior scrollBehavior = ScrollBehaviorAuto;
     if (!scrollBehaviorFromScrollOptions(scrollOptions, scrollBehavior, exceptionState))
         return;
     scrollTo(x, y, scrollBehavior);
@@ skipping 503 matching lines @@
     FrameDestructionObserver::trace(visitor);
 }
 
 v8::Handle<v8::Object> LocalDOMWindow::wrap(v8::Handle<v8::Object> creationContext, v8::Isolate* isolate)
 {
     ASSERT_NOT_REACHED(); // LocalDOMWindow has [Custom=ToV8].
     return v8::Handle<v8::Object>();
 }
 
 } // namespace blink