Bug 1424474 part 1. Make sure we don't call into the chrome registry's AllowContentToAccess with non-chrome URLs. r=gijs

MozReview-Commit-ID: I3DyrYGpGC2

caps/nsScriptSecurityManager.cpp

@@ -897,7 +897,7 @@ nsScriptSecurityManager::CheckLoadURIFlags(nsIURI *aSourceURI,
                 if (accessAllowed) {
                     return NS_OK;
                 }
-            } else {
+            } else if (targetScheme.EqualsLiteral("chrome")) {
                 // Allow the load only if the chrome package is whitelisted.
                 nsCOMPtr<nsIXULChromeRegistry> reg(
                         do_GetService(NS_CHROMEREGISTRY_CONTRACTID));