Initialize GPU shader disk cache on brower thread.

content/public/browser/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 CONTENT_PUBLIC_BROWSER_CONTENT_BROWSER_CLIENT_H_
 #define CONTENT_PUBLIC_BROWSER_CONTENT_BROWSER_CLIENT_H_
 
 #include <map>
 #include <string>
 #include <utility>
@@ skipping 496 matching lines @@
   virtual void ClearCookies(RenderFrameHost* rfh) {}
 
   // Returns the default download directory.
   // This can be called on any thread.
   virtual base::FilePath GetDefaultDownloadDirectory();
 
   // Returns the default filename used in downloads when we have no idea what
   // else we should do with the file.
   virtual std::string GetDefaultDownloadName();
 
+  // Returns the path to the browser shader disk cache root.

[jam, 2015/08/07 20:41:04]

nit: please make chrome return a path that includes the shader directory (i.e.
not root = udd). i would like to avoid sending udd directly to content module to
avoid layering violations with content mucking with chrome's files

[Jamie Madill, 2015/08/10 17:18:00]

Done.

+  virtual base::FilePath GetShaderDiskCacheDirectory();
+
   // Notification that a pepper plugin has just been spawned. This allows the
   // embedder to add filters onto the host to implement interfaces.
   // This is called on the IO thread.
   virtual void DidCreatePpapiPlugin(BrowserPpapiHost* browser_host) {}
 
   // Gets the host for an external out-of-process plugin.
   virtual BrowserPpapiHost* GetExternalBrowserPpapiHost(
       int plugin_child_id);
 
   // Returns true if the socket operation specified by |params| is allowed from
@@ skipping 149 matching lines @@
   // Allows an embedder to provide its own ExternalVideoSurfaceContainer
   // implementation.  Return nullptr to disable external surface video.
   virtual ExternalVideoSurfaceContainer*
   OverrideCreateExternalVideoSurfaceContainer(WebContents* web_contents);
 #endif
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_CONTENT_BROWSER_CLIENT_H_