fix($rootScope): Internal state consistency

During a recursive $apply, clear the state only if the state was set in
that call.

Author: lgalfaso

src/ng/rootScope.js

@@ -1038,13 +1038,17 @@ function $RootScopeProvider() {
        * @returns {*} The result of evaluating the expression.
        */
       $apply: function(expr) {
+        var doCleanPhase = false;
         try {
           beginPhase('$apply');
+          doCleanPhase = true;
           return this.$eval(expr);
         } catch (e) {
           $exceptionHandler(e);
         } finally {
-          clearPhase();
+          if (doCleanPhase) {
+            clearPhase();
+          }
           try {
             $rootScope.$digest();
           } catch (e) {

test/ng/rootScopeSpec.js

@@ -1505,6 +1505,19 @@ describe('Scope', function() {
       }));
 
 
+      it('should not clear the state when calling $apply during an $apply', inject(
+          function($rootScope) {
+        $rootScope.$apply(function() {
+          expect(function() {
+            $rootScope.$apply();
+          }).toThrowMinErr('$rootScope', 'inprog', '$apply already in progress');
+          expect(function() {
+            $rootScope.$apply();
+          }).toThrowMinErr('$rootScope', 'inprog', '$apply already in progress');
+        });
+      }));
+
+
       it('should throw an exception if $apply is called while flushing evalAsync queue', inject(
           function($rootScope) {
         expect(function() {