Initialize GPU shader disk cache on brower thread.

chrome/browser/chrome_content_browser_client.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 CHROME_BROWSER_CHROME_CONTENT_BROWSER_CLIENT_H_
 #define CHROME_BROWSER_CHROME_CONTENT_BROWSER_CLIENT_H_
 
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 202 matching lines @@
   net::NetLog* GetNetLog() override;
   content::AccessTokenStore* CreateAccessTokenStore() override;
   bool IsFastShutdownPossible() override;
   void OverrideWebkitPrefs(content::RenderViewHost* rvh,
                            content::WebPreferences* prefs) override;
   void BrowserURLHandlerCreated(content::BrowserURLHandler* handler) override;
   void ClearCache(content::RenderFrameHost* rfh) override;
   void ClearCookies(content::RenderFrameHost* rfh) override;
   base::FilePath GetDefaultDownloadDirectory() override;
   std::string GetDefaultDownloadName() override;
+  base::FilePath GetUserDataDirectory() override;
   void DidCreatePpapiPlugin(content::BrowserPpapiHost* browser_host) override;
   content::BrowserPpapiHost* GetExternalBrowserPpapiHost(
       int plugin_process_id) override;
   bool AllowPepperSocketAPI(
       content::BrowserContext* browser_context,
       const GURL& url,
       bool private_api,
       const content::SocketPermissionRequest* params) override;
   ui::SelectFilePolicy* CreateSelectFilePolicy(
       content::WebContents* web_contents) override;
@@ skipping 96 matching lines @@
   std::vector<ChromeContentBrowserClientParts*> extra_parts_;
 
   base::WeakPtrFactory<ChromeContentBrowserClient> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeContentBrowserClient);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_CHROME_CONTENT_BROWSER_CLIENT_H_