Don't show the search-by-image menu item when the image is blocked (no image pixel data)

chrome/browser/renderer_host/chrome_render_view_host_observer.cc

 // Copyright (c) 2012 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/browser/renderer_host/chrome_render_view_host_observer.h"
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/strings/stringprintf.h"
@@ skipping 188 matching lines @@
 #if defined(OS_WIN) && defined(USE_AURA)
     base::win::DismissVirtualKeyboard();
 #endif
   }
 }
 
 // Handles the image thumbnail for the context node, composes a image search
 // request based on the received thumbnail and opens the request in a new tab.
 void ChromeRenderViewHostObserver::OnRequestThumbnailForContextNodeACK(
     const SkBitmap& bitmap) {
+  if (bitmap.isNull())
+    return;
   WebContents* web_contents =
       WebContents::FromRenderViewHost(render_view_host());
   const TemplateURL* const default_provider =
       TemplateURLServiceFactory::GetForProfile(profile_)->
           GetDefaultSearchProvider();
   if (!web_contents || !default_provider)
     return;
 
   const int kDefaultQualityForImageSearch = 90;
   std::vector<unsigned char> data;
@@ skipping 24 matching lines @@
     DCHECK(!content_type.empty());
     open_url_params.uses_post = true;
     open_url_params.browser_initiated_post_data =
         base::RefCountedString::TakeString(post_data);
     open_url_params.extra_headers += base::StringPrintf(
         "%s: %s\r\n", net::HttpRequestHeaders::kContentType,
         content_type.c_str());
   }
   web_contents->OpenURL(open_url_params);
 }