[extensions] Stop parsing webstore urls so much

chrome/common/extensions/chrome_extensions_client.h

Index: chrome/common/extensions/chrome_extensions_client.h
diff --git a/chrome/common/extensions/chrome_extensions_client.h b/chrome/common/extensions/chrome_extensions_client.h
index b75404ad111afed2ee02dfc073f5c57b96b2a451..87b8f828f74d52fdddc6e40ea55ae430397825eb 100644
--- a/chrome/common/extensions/chrome_extensions_client.h
+++ b/chrome/common/extensions/chrome_extensions_client.h
@@ -14,6 +14,7 @@
 #include "chrome/common/extensions/permissions/chrome_permission_message_provider.h"
 #include "extensions/common/extensions_client.h"
 #include "extensions/common/permissions/extensions_api_permissions.h"
+#include "url/gurl.h"
 
 namespace extensions {
 
@@ -47,7 +48,7 @@ class ChromeExtensionsClient : public ExtensionsClient {
   bool ShouldSuppressFatalErrors() const override;
   void RecordDidSuppressFatalError() override;
   std::string GetWebstoreBaseURL() const override;
-  std::string GetWebstoreUpdateURL() const override;
+  const GURL& GetWebstoreUpdateURL() const override;
   bool IsBlacklistUpdateURL(const GURL& url) const override;
   std::set<base::FilePath> GetBrowserImagePaths(
       const Extension* extension) override;
@@ -67,6 +68,9 @@ class ChromeExtensionsClient : public ExtensionsClient {
   // added to this list.
   ScriptingWhitelist scripting_whitelist_;
 
+  // Mutable to allow caching in a const method.
+  mutable GURL webstore_update_url_;
+
   friend struct base::DefaultLazyInstanceTraits<ChromeExtensionsClient>;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeExtensionsClient);