fix($animate): remove the need to add display:block!important for ngShow/ngHide

Since ngShow/ngHide animations add and remove the .ng-hide class, having to remember
to write display:block on your own is a hassle and leads to problematic animation
code. This fix places a default on the animation for you instead.

Closes #3813

css/angular.css

@@ -14,3 +14,9 @@ ng\:form {
   transition:0s all!important;
   -webkit-transition:0s all!important;
 }
+
+/* show the element during a show/hide animation when the
+ * animation is ongoing, but the .ng-hide class is active */
+.ng-hide-add-active, .ng-hide-remove {
+  display: block!important;
+}

src/ng/directive/ngShowHide.js

@@ -40,10 +40,8 @@
  * restating the styles for the .ng-hide class in CSS:
  * ```css
  * .ng-hide {
- *   //!annotate CSS Specificity|Not to worry, this will override the AngularJS default...
+ *   /* this is just another form of hiding an element */
  *   display:block!important;
- *
- *   //this is just another form of hiding an element
  *   position:absolute;
  *   top:-9999px;
  *   left:-9999px;
@@ -70,7 +68,6 @@
  * //
  * .my-element.ng-hide-add, .my-element.ng-hide-remove {
  *   transition:0.5s linear all;
- *   display:block!important;
  * }
  *
  * .my-element.ng-hide-add { ... }
@@ -118,11 +115,6 @@
         background:white;
       }
 
-      .animate-show.ng-hide-add,
-      .animate-show.ng-hide-remove {
-        display:block!important;
-      }
-
       .animate-show.ng-hide {
         line-height:0;
         opacity:0;
@@ -200,9 +192,6 @@ var ngShowDirective = ['$animate', function($animate) {
  * restating the styles for the .ng-hide class in CSS:
  * ```css
  * .ng-hide {
- *   //!annotate CSS Specificity|Not to worry, this will override the AngularJS default...
- *   display:block!important;
- *
  *   //this is just another form of hiding an element
  *   position:absolute;
  *   top:-9999px;
@@ -230,7 +219,6 @@ var ngShowDirective = ['$animate', function($animate) {
  * //
  * .my-element.ng-hide-add, .my-element.ng-hide-remove {
  *   transition:0.5s linear all;
- *   display:block!important;
  * }
  *
  * .my-element.ng-hide-add { ... }
@@ -278,11 +266,6 @@ var ngShowDirective = ['$animate', function($animate) {
         background:white;
       }
 
-      .animate-hide.ng-hide-add,
-      .animate-hide.ng-hide-remove {
-        display:block!important;
-      }
-
       .animate-hide.ng-hide {
         line-height:0;
         opacity:0;