Bug 1390170 - DOMException.prototype should have .message and .name r=bkelly

The spec requires that they be interface members:

  https://heycam.github.io/webidl/#idl-DOMException

This means they're on the prototype.  This change brings us in line with
Chrome, Edge, and WebKit, as tested by
<https://github.com/w3c/web-platform-tests/pull/6875>.

MozReview-Commit-ID: A1cKpmlCNCs

--HG--
extra : rebase_source : 1bce93cdb44fe6718289a86314bbe8ab4afea6ed

dom/webidl/DOMException.webidl

@@ -19,12 +19,8 @@ interface StackFrame;
  Exposed=(Window,Worker)]
 interface ExceptionMembers
 {
-  // A custom message set by the thrower.
-  readonly attribute DOMString               message;
   // The nsresult associated with this exception.
   readonly attribute unsigned long           result;
-  // The name of the error code (ie, a string repr of |result|).
-  readonly attribute DOMString               name;
 
   // Filename location.  This is the location that caused the
   // error, which may or may not be a source file location.
@@ -57,6 +53,10 @@ interface ExceptionMembers
 
 [NoInterfaceObject, Exposed=(Window,Worker)]
 interface Exception {
+  // The name of the error code (ie, a string repr of |result|).
+  readonly attribute DOMString               name;
+  // A custom message set by the thrower.
+  readonly attribute DOMString               message;
   // A generic formatter - make it suitable to print, etc.
   stringifier;
 };
@@ -69,6 +69,12 @@ Exception implements ExceptionMembers;
  Exposed=(Window, Worker),
  Constructor(optional DOMString message = "", optional DOMString name)]
 interface DOMException {
+  // The name of the error code (ie, a string repr of |result|).
+  readonly attribute DOMString               name;
+  // A custom message set by the thrower.
+  readonly attribute DOMString               message;
+  readonly attribute unsigned short code;
+
   const unsigned short INDEX_SIZE_ERR = 1;
   const unsigned short DOMSTRING_SIZE_ERR = 2; // historical
   const unsigned short HIERARCHY_REQUEST_ERR = 3;
@@ -94,8 +100,6 @@ interface DOMException {
   const unsigned short TIMEOUT_ERR = 23;
   const unsigned short INVALID_NODE_TYPE_ERR = 24;
   const unsigned short DATA_CLONE_ERR = 25;
-
-  readonly attribute unsigned short code;
 };
 
 // XXXkhuey copy all of Gecko's non-standard stuff onto DOMException, but leave