fix(ngMocks): allow ErrorAddingDeclarationLocationStack to be recognized as an Error

Change `ErrorAddingDeclarationLocationStack`'s prototype so test frameworks (such as Jasmine 2.x)
are able to recognize it as `Error`.

Fixes #13821

Closes #14344

Author: peabnuts123

src/ngMock/angular-mocks.js

@@ -3057,7 +3057,7 @@ angular.mock.$RootScopeDecorator = ['$delegate', function($delegate) {
       this.stack = e.stack + '\n' + errorForStack.stack;
     if (e.stackArray) this.stackArray = e.stackArray;
   };
-  ErrorAddingDeclarationLocationStack.prototype.toString = Error.prototype.toString;
+  ErrorAddingDeclarationLocationStack.prototype = Error.prototype;
 
   window.inject = angular.mock.inject = function() {
     var blockFns = Array.prototype.slice.call(arguments, 0);

test/ngMock/angular-mocksSpec.js

@@ -631,7 +631,6 @@ describe('ngMock', function() {
 
       inject(); // Trigger the tests in `module`
     });
-
   });
 
 
@@ -985,6 +984,22 @@ describe('ngMock', function() {
           });
         }
       });
+
+      describe('ErrorAddingDeclarationLocationStack', function() {
+        it('should be caught by Jasmine\'s `toThrowError()`', function() {
+          function throwErrorAddingDeclarationStack() {
+            module(function($provide) {
+              $provide.factory('badFactory', function() {
+                throw new Error('BadFactoryError');
+              });
+            });
+
+            inject(function(badFactory) {});
+          }
+
+          expect(throwErrorAddingDeclarationStack).toThrowError(/BadFactoryError/);
+        });
+      });
     });
   });
 
@@ -2616,8 +2631,10 @@ describe('make sure that we can create an injector outside of tests', function()
   angular.injector([function($injector) {}]);
 });
 
+
 describe('`afterEach` clean-up', function() {
   describe('`$rootElement`', function() {
+
     describe('undecorated', function() {
       var prevRootElement;
       var prevCleanDataSpy;
@@ -2780,6 +2797,7 @@ describe('`afterEach` clean-up', function() {
   });
 });
 
+
 describe('sharedInjector', function() {
   // this is of a bit tricky feature to test as we hit angular's own testing
   // mechanisms (e.g around jQuery cache checking), as ngMock augments the very
@@ -3037,5 +3055,4 @@ describe('sharedInjector', function() {
     if (typeof fn !== "function") throw Error("not fn", fn);
     sdescribe.current.afterEach.push(fn);
   }
-
 });