Re-enabling the fix for bug 69070 and optimizing some string code in caps that was for sure part of the reason for the Tp regression, and use CheckLoadURIWithPrincipal() to be more correct. r+sr=bzbarsky@mit.edu

caps/include/nsScriptSecurityManager.h

@@ -346,8 +346,8 @@ private:
     static nsresult
     doGetObjectPrincipal(JSContext *cx, JSObject *obj, nsIPrincipal **result);
 
-    nsresult
-    GetBaseURIScheme(nsIURI* aURI, char** aScheme);
+    static nsresult
+    GetBaseURIScheme(nsIURI* aURI, nsCString& aScheme);
 
     static nsresult 
     ReportError(JSContext* cx, const nsAString& messageTag,