Replace ASSERT with DCHECK in core/

third_party/WebKit/Source/core/frame/RootFrameViewport.h

 // 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.
 
 #ifndef RootFrameViewport_h
 #define RootFrameViewport_h
 
 #include "core/CoreExport.h"
 #include "platform/scroll/ScrollableArea.h"
 
@@ skipping 106 matching lines @@
                                         ScrollType,
                                         ScrollBehavior,
                                         ViewportToScrollFirst);
 
   // If either of the layout or visual viewports are scrolled explicitly (i.e.
   // not through this class), their updated offset will not be reflected in this
   // class' animator so use this method to pull updated values when necessary.
   void UpdateScrollAnimator();
 
   ScrollableArea& VisualViewport() const {
-    ASSERT(visual_viewport_);
+    DCHECK(visual_viewport_);
     return *visual_viewport_;
   }
 
   Member<ScrollableArea> visual_viewport_;
   Member<ScrollableArea> layout_viewport_;
 };
 
 DEFINE_TYPE_CASTS(RootFrameViewport,
                   ScrollableArea,
                   scrollableArea,
                   scrollableArea->IsRootFrameViewport(),
                   scrollableArea.IsRootFrameViewport());
 
 }  // namespace blink
 
 #endif  // RootFrameViewport_h