chore(): move hardcoded priority value to a constant (#9791)

There are several directives that are supposed to run before `ngAria` and who have a hardcoded priority of 210. This change moves the priority to a constant so it's easier to maintain.

Author: crisbeto

src/components/checkbox/checkbox.js

@@ -61,7 +61,7 @@ function MdCheckboxDirective(inputDirective, $mdAria, $mdConstant, $mdTheming, $
     restrict: 'E',
     transclude: true,
     require: '?ngModel',
-    priority: 210, // Run before ngAria
+    priority: $mdConstant.BEFORE_NG_ARIA,
     template:
       '<div class="md-container" md-ink-ripple md-ink-ripple-checkbox>' +
         '<div class="md-icon"></div>' +

src/components/menuBar/js/menuItemDirective.js

@@ -4,11 +4,11 @@ angular
   .directive('mdMenuItem', MenuItemDirective);
 
  /* @ngInject */
-function MenuItemDirective($mdUtil, $$mdSvgRegistry) {
+function MenuItemDirective($mdUtil, $mdConstant, $$mdSvgRegistry) {
   return {
     controller: 'MenuItemController',
     require: ['mdMenuItem', '?ngModel'],
-    priority: 210, // ensure that our post link runs after ngAria
+    priority: $mdConstant.BEFORE_NG_ARIA,
     compile: function(templateEl, templateAttrs) {
       var type = templateAttrs.type;
       var inMenuBarClass = 'md-in-menu-bar';

src/components/switch/switch.js

@@ -51,7 +51,7 @@ function MdSwitch(mdCheckboxDirective, $mdUtil, $mdConstant, $parse, $$rAF, $mdG
 
   return {
     restrict: 'E',
-    priority: 210, // Run before ngAria
+    priority: $mdConstant.BEFORE_NG_ARIA,
     transclude: true,
     template:
       '<div class="md-container">' +

src/components/tooltip/tooltip.js

@@ -35,7 +35,7 @@ angular
  * @param {string=} md-direction Which direction would you like the tooltip to go?  Supports left, right, top, and bottom.  Defaults to bottom.
  */
 function MdTooltipDirective($timeout, $window, $$rAF, $document, $mdUtil, $mdTheming, $animate,
-  $interpolate, $$mdTooltipRegistry) {
+  $interpolate, $mdConstant, $$mdTooltipRegistry) {
 
   var ENTER_EVENTS = 'focus touchstart mouseenter';
   var LEAVE_EVENTS = 'blur touchcancel mouseleave';
@@ -46,7 +46,7 @@ function MdTooltipDirective($timeout, $window, $$rAF, $document, $mdUtil, $mdThe
   return {
     restrict: 'E',
     transclude: true,
-    priority: 210, // Before ngAria
+    priority: $mdConstant.BEFORE_NG_ARIA,
     template: '<div class="md-content _md" ng-transclude></div>',
     scope: {
       delay: '=?mdDelay',

src/core/util/constant.js

@@ -38,7 +38,7 @@ function MdConstantFactory($sniffer, $window, $document) {
     isNumPadKey : function (e){ return (3 === e.location && e.keyCode >= 97 && e.keyCode <= 105); },
     isNavigationKey : function(e) {
       var kc = self.KEY_CODE, NAVIGATION_KEYS =  [kc.SPACE, kc.ENTER, kc.UP_ARROW, kc.DOWN_ARROW];
-      return (NAVIGATION_KEYS.indexOf(e.keyCode) != -1);    
+      return (NAVIGATION_KEYS.indexOf(e.keyCode) != -1);
     },
 
     /**
@@ -49,6 +49,11 @@ function MdConstantFactory($sniffer, $window, $document) {
      */
     ELEMENT_MAX_PIXELS: 1533917,
 
+    /**
+     * Priority for a directive that should run before the directives from ngAria.
+     */
+    BEFORE_NG_ARIA: 210,
+
     /**
      * Common Keyboard actions and their associated keycode.
      */