docs(*): Document a lot more symbols that are missing comments in our generated docs.

modules/angular2/src/mock/directive_resolver_mock.ts

@@ -4,6 +4,10 @@ import {Type, isPresent, stringify, isBlank, print} from 'angular2/src/facade/la
 import {DirectiveMetadata, ComponentMetadata} from '../core/metadata';
 import {DirectiveResolver} from 'angular2/src/core/linker/directive_resolver';
 
+/**
+ * An implementation of {@link DirectiveResolver} that allows overriding
+ * various properties of directives.
+ */
 @Injectable()
 export class MockDirectiveResolver extends DirectiveResolver {
   private _providerOverrides = new Map<Type, any[]>();

modules/angular2/src/mock/location_mock.ts

@@ -3,6 +3,9 @@ import {EventEmitter, ObservableWrapper} from 'angular2/src/facade/async';
 import {ListWrapper} from 'angular2/src/facade/collection';
 import {Location} from 'angular2/src/router/location';
 
+/**
+ * A spy for {@link Location} that allows tests to fire simulated location events.
+ */
 @Injectable()
 export class SpyLocation implements Location {
   urlChanges: string[] = [];

modules/angular2/src/mock/mock_application_ref.ts

@@ -6,6 +6,9 @@ import {Provider, Injector} from 'angular2/src/core/di';
 import {NgZone} from 'angular2/src/core/zone/ng_zone';
 import {Promise} from 'angular2/src/facade/async';
 
+/**
+ * A no-op implementation of {@link ApplicationRef}, useful for testing.
+ */
 @Injectable()
 export class MockApplicationRef extends ApplicationRef {
   registerBootstrapListener(listener: (ref: ComponentRef) => void): void {}

modules/angular2/src/mock/mock_location_strategy.ts

@@ -3,6 +3,10 @@ import {EventEmitter, ObservableWrapper} from 'angular2/src/facade/async';
 import {LocationStrategy} from 'angular2/src/router/location_strategy';
 
 
+/**
+ * A mock implementation of {@link LocationStrategy} that allows tests to fire simulated
+ * location events.
+ */
 @Injectable()
 export class MockLocationStrategy extends LocationStrategy {
   internalBaseHref: string = '/';

modules/angular2/src/mock/ng_zone_mock.ts

@@ -2,6 +2,9 @@ import {Injectable} from 'angular2/src/core/di';
 import {NgZone} from 'angular2/src/core/zone/ng_zone';
 import {EventEmitter, ObservableWrapper} from 'angular2/src/facade/async';
 
+/**
+ * A mock implementation of {@link NgZone}.
+ */
 @Injectable()
 export class MockNgZone extends NgZone {
   /** @internal */