Bug 1122463 - Don't blur the input when submit is cancelled. r=yxl

--HG--
extra : rebase_source : 02b5f6bdd130c58355371cce630f58e00647b4d7

dom/inputmethod/forms.js

@@ -193,7 +193,9 @@ let FormAssistant = {
     addEventListener("focus", this, true, false);
     addEventListener("blur", this, true, false);
     addEventListener("resize", this, true, false);
-    addEventListener("submit", this, true, false);
+    // We should not blur the fucus if the submit event is cancelled,
+    // therefore we are binding our event listener in the bubbling phase here.
+    addEventListener("submit", this, false, false);
     addEventListener("pagehide", this, true, false);
     addEventListener("beforeunload", this, true, false);
     addEventListener("input", this, true, false);
@@ -399,7 +401,7 @@ let FormAssistant = {
         }
         // fall through
       case "submit":
-        if (this.focusedElement) {
+        if (this.focusedElement && !evt.defaultPrevented) {
           this.focusedElement.blur();
         }
         break;