Bug 755558 - report exceptions in head.js during browser-test. r=gavin

testing/mochitest/browser-test.js

@@ -306,7 +306,14 @@ Tester.prototype = {
     var headPath = currentTestDirPath + "/head.js";
     try {
       this._scriptLoader.loadSubScript(headPath, this.currentTest.scope);
-    } catch (ex) { /* no head */ }
+    } catch (ex) {
+      // Ignore if no head.js exists, but report all other errors.  Note this
+      // will also ignore an existing head.js attempting to import a missing
+      // module - see bug 755558 for why this strategy is preferred anyway.
+      if (ex.toString() != 'Error opening input stream (invalid filename?)') {
+       this.currentTest.addResult(new testResult(false, "head.js import threw an exception", ex, false));
+      }
+    }
 
     // Import the test script.
     try {