fix(virtualRepeat): Resolve bizarre missing $scope.$root issue (#6129)

Closes #6171

src/components/virtualRepeat/virtual-repeater.js

@@ -80,7 +80,8 @@ var NUM_EXTRA = 3;
 
 /** @ngInject */
 function VirtualRepeatContainerController(
-    $$rAF, $mdUtil, $parse, $window, $scope, $element, $attrs) {
+    $$rAF, $mdUtil, $parse, $rootScope, $window, $scope, $element, $attrs) {
+  this.$rootScope = $rootScope;
   this.$scope = $scope;
   this.$element = $element;
   this.$attrs = $attrs;
@@ -339,7 +340,7 @@ VirtualRepeatContainerController.prototype.handleScroll_ = function() {
     if (topIndex !== this.topIndex && topIndex < this.repeater.itemsLength) {
       this.topIndex = topIndex;
       this.bindTopIndex.assign(this.$scope, topIndex);
-      if (!this.$scope.$root.$$phase) this.$scope.$digest();
+      if (!this.$rootScope.$$phase) this.$scope.$digest();
     }
   }
 
@@ -413,12 +414,14 @@ function VirtualRepeatDirective($parse) {
 
 
 /** @ngInject */
-function VirtualRepeatController($scope, $element, $attrs, $browser, $document, $$rAF) {
+function VirtualRepeatController($scope, $element, $attrs, $browser, $document, $rootScope,
+    $$rAF) {
   this.$scope = $scope;
   this.$element = $element;
   this.$attrs = $attrs;
   this.$browser = $browser;
   this.$document = $document;
+  this.$rootScope = $rootScope;
   this.$$rAF = $$rAF;
 
   /** @type {boolean} Whether we are in on-demand mode. */
@@ -559,7 +562,7 @@ VirtualRepeatController.prototype.containerUpdated = function() {
             this.$$rAF(angular.bind(this, this.readItemSize_));
           }
         }));
-    if (!this.$scope.$root.$$phase) this.$scope.$digest();
+    if (!this.$rootScope.$$phase) this.$scope.$digest();
 
     return;
   } else if (!this.sized) {
@@ -750,7 +753,7 @@ VirtualRepeatController.prototype.updateBlock_ = function(block, index) {
   // Perform digest before reattaching the block.
   // Any resulting synchronous dom mutations should be much faster as a result.
   // This might break some directives, but I'm going to try it for now.
-  if (!this.$scope.$root.$$phase) {
+  if (!this.$rootScope.$$phase) {
     block.scope.$digest();
   }
 };