DevTools: request page thumbnails from the devtools handler delegate, do not redirect to chrome://t…

content/public/browser/devtools_http_handler_delegate.h

 // 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_DEVTOOLS_HTTP_HANDLER_DELEGATE_H_
 #define CONTENT_PUBLIC_BROWSER_DEVTOOLS_HTTP_HANDLER_DELEGATE_H_
 
 #include <string>
 #include <vector>
 
+class GURL;
+
 namespace content {
 
 class WebContents;
 
 class DevToolsHttpHandlerDelegate {
  public:
   virtual ~DevToolsHttpHandlerDelegate() {}
 
   // Should return discovery page HTML that should list available tabs
   // and provide attach links. Called on the IO thread.
   virtual std::string GetDiscoveryPageHTML() = 0;
 
   // Returns true if and only if frontend resources are bundled.
   virtual bool BundlesFrontendResources() = 0;
 
   // Returns URL that front-end files are available at, empty string if
   // no internal server is available.
   virtual std::string GetFrontendResourcesBaseURL() = 0;
+
+  // Get a thumbnail for a given page. Returns non-empty string iff we have the
+  // thumbnail.
+  virtual std::string GetPageThumbnailData(const GURL& url) = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_DEVTOOLS_HTTP_HANDLER_DELEGATE_H_