Avoid parsing the webstore base url so much.

extensions/shell/common/shell_extensions_client.h

Index: extensions/shell/common/shell_extensions_client.h
diff --git a/extensions/shell/common/shell_extensions_client.h b/extensions/shell/common/shell_extensions_client.h
index b9bb22c677013168e59970f815979391cd5e9753..baea44073ad292e2d01ebaf70ae7639829e1e6c2 100644
--- a/extensions/shell/common/shell_extensions_client.h
+++ b/extensions/shell/common/shell_extensions_client.h
@@ -41,7 +41,7 @@ class ShellExtensionsClient : public ExtensionsClient {
   base::StringPiece GetAPISchema(const std::string& name) const override;
   bool ShouldSuppressFatalErrors() const override;
   void RecordDidSuppressFatalError() override;
-  std::string GetWebstoreBaseURL() const override;
+  const GURL& GetWebstoreBaseURL() const override;
   const GURL& GetWebstoreUpdateURL() const override;
   bool IsBlacklistUpdateURL(const GURL& url) const override;
 
@@ -50,6 +50,7 @@ class ShellExtensionsClient : public ExtensionsClient {
 
   ScriptingWhitelist scripting_whitelist_;
 
+  const GURL webstore_base_url_;
   const GURL webstore_update_url_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellExtensionsClient);