Initialize GPU shader disk cache on brower thread.

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index 17b00c74b490b1b7c99d0d141c5121db6c4de03a..cadc2bc89f51e56ee1bbbd3c273d6fa0d08f7ae4 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -2264,6 +2264,13 @@ std::string ChromeContentBrowserClient::GetDefaultDownloadName() {
   return l10n_util::GetStringUTF8(IDS_DEFAULT_DOWNLOAD_FILENAME);
 }
 
+base::FilePath ChromeContentBrowserClient::GetShaderDiskCacheDirectory() {
+  base::FilePath user_data_dir;
+  PathService::Get(DIR_USER_DATA, &user_data_dir);
+  DCHECK(!user_data_dir.empty());
+  return user_data_dir.Append(FILE_PATH_LITERAL("ShaderCache"));
+}
+
 void ChromeContentBrowserClient::DidCreatePpapiPlugin(
     content::BrowserPpapiHost* browser_host) {
 #if defined(ENABLE_PLUGINS)