Bug 1275078 - toolbox-init.js error handling tweaks from Positron. r=ochameau

MozReview-Commit-ID: LDjzdUTJikc

--HG--
extra : rebase_source : 7e6c96f9543f14f07c00ee79d9a3796292c7d04f

devtools/client/framework/toolbox-init.js

@@ -58,12 +58,15 @@ if (url.search.length > 1) {
       // `iframe` is the targeted document to debug
       let iframe = host.wrappedJSObject ? host.wrappedJSObject.target
                                         : host.target;
+      if (!iframe) {
+        throw new Error("Unable to find the targeted iframe to debug");
+      }
+
       // Need to use a xray and query some interfaces to have
       // attributes and behavior expected by devtools codebase
       iframe = XPCNativeWrapper(iframe);
       iframe.QueryInterface(Ci.nsIFrameLoaderOwner);
 
-      if (iframe) {
       // Fake a xul:tab object as we don't have one.
       // linkedBrowser is the only one attribute being queried by client.getTab
       let tab = { linkedBrowser: iframe };
@@ -79,9 +82,6 @@ if (url.search.length > 1) {
       let response = yield client.getTab({ tab });
       let form = response.tab;
       target = yield TargetFactory.forRemoteTab({client, form, chrome: false});
-      } else {
-        alert("Unable to find the targetted iframe to debug");
-      }
     } else {
       target = yield targetFromURL(url);
     }