[Mac] Don't paint linen pattern when contents size is not available.

chrome/browser/renderer_host/render_widget_host_view_mac.mm

 // Copyright (c) 2011 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 <QuartzCore/QuartzCore.h>
 
 #include "chrome/browser/renderer_host/render_widget_host_view_mac.h"
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
@@ skipping 1622 matching lines @@
       NSMakeRect(-offset.x(), -offset.y(), size.width(), size.height());
   NSRect frameRect = [self frame];
   frameRect.origin = NSMakePoint(0, 0);
   return NSIntersectionRect(frameRect, contentRect);
 }
 
 - (void)fillOverScrollAreas:(NSRect)dirtyRect {
   if (![NSColor respondsToSelector:@selector(_linenPatternImage)])
     return;
 
+  // Don't paint over-scroll areas if |contents_size| is empty, which indicates
+  // that the render widget is not a RenderView.
+  if (renderWidgetHostView_->render_widget_host_->contents_size().IsEmpty())
+    return;
+
   NSRect visibleContentRect = [self computeVisibleContentRect];
   NSSize frameSize = [self frame].size;
   bool hasHorizontalOverflow = (NSWidth(visibleContentRect) < frameSize.width);
   bool hasVerticalOverflow = (NSHeight(visibleContentRect) < frameSize.height);
 
   if (!hasHorizontalOverflow && !hasVerticalOverflow)
     return;
 
   NSRect xRect = NSMakeRect(0,
                             0,
@@ skipping 1103 matching lines @@
   if (!string) return NO;
 
   // If the user is currently using an IME, confirm the IME input,
   // and then insert the text from the service, the same as TextEdit and Safari.
   [self confirmComposition];
   [self insertText:string];
   return YES;
 }
 
 @end