Fix null pointer exception in WebViewColorOverlay.

chrome/renderer/webview_color_overlay.cc

 // 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 "chrome/renderer/webview_color_overlay.h"
 
 #include "base/logging.h"
 #include "content/public/renderer/render_view.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "third_party/skia/include/core/SkRect.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebView.h"
 #include "ui/gfx/size.h"
 #include "ui/gfx/skia_util.h"
 
 #if WEBKIT_USING_CG
 #include "skia/ext/skia_utils_mac.h"
 #endif
 
 WebViewColorOverlay::WebViewColorOverlay(content::RenderView* render_view,
                                          SkColor color)
     : render_view_(render_view),
       color_(color) {
   render_view_->GetWebView()->addPageOverlay(this, 0);
 }
 
 WebViewColorOverlay::~WebViewColorOverlay() {
-  render_view_->GetWebView()->removePageOverlay(this);
+  if (render_view_->GetWebView())
+    render_view_->GetWebView()->removePageOverlay(this);
 }
 
 void WebViewColorOverlay::paintPageOverlay(WebKit::WebCanvas* canvas) {
   SkRect rect = gfx::RectToSkRect(gfx::Rect(render_view_->GetSize()));
 
 #if WEBKIT_USING_SKIA
   SkPaint paint;
   paint.setColor(color_);
   paint.setStyle(SkPaint::kFill_Style);
   canvas->drawRect(rect, paint);
 #elif WEBKIT_USING_CG
   CGContextSaveGState(canvas);
   CGColorRef color = gfx::SkColorToCGColorRef(color_);
   CGContextSetFillColorWithColor(canvas, color);
   CGColorRelease(color);
   CGContextFillRect(canvas, gfx::SkRectToCGRect(rect));
   CGContextRestoreGState(canvas);
 #else
   NOTIMPLEMENTED();
 #endif
 }