docs(di): add missing docs

Closes #4302

modules/angular2/src/core/di/binding.ts

@@ -254,6 +254,9 @@ export class Binding {
  * ```
  */
 export class ResolvedBinding {
+  /**
+   * @private
+   */
   constructor(
       /**
        * A key, usually a `Type`.
@@ -261,11 +264,13 @@ export class ResolvedBinding {
       public key: Key,
 
       /**
+       * @private
        * Factory function which can return an instance of an object represented by a key.
        */
       public resolvedFactories: ResolvedFactory[],
 
       /**
+       * @private
        * Indicates if the binding is a multi-binding or a regular binding.
        */
       public multiBinding: boolean) {}
@@ -275,6 +280,7 @@ export class ResolvedBinding {
 }
 
 /**
+ * @private
  * An internal resolved representation of a factory function created by resolving {@link Binding}.
  */
 export class ResolvedFactory {

modules/angular2/src/core/di/forward_ref.ts

@@ -1,5 +1,14 @@
 import {Type, stringify, isFunction} from 'angular2/src/core/facade/lang';
 
+/**
+ * An interface that a function passed into {@link forwardRef} has to implement.
+ *
+ * ### Example
+ *
+ * ```typescript
+ * var fn:ForwardRefFn = forwardRef(() => Lock);
+ * ```
+ */
 export interface ForwardRefFn { (): any; }
 
 /**

modules/angular2/src/core/di/metadata.ts

@@ -74,29 +74,7 @@ export class OptionalMetadata {
 
 /**
  * `DependencyMetadata` is used by the framework to extend DI.
- *
- * Only metadata implementing `DependencyMetadata` are added to the list of dependency
- * properties.
- *
- * For example:
- *
- * ```
- * class Exclude extends DependencyMetadata {}
- * class NotDependencyProperty {}
- *
- * class AComponent {
- *   constructor(@Exclude @NotDependencyProperty aService:AService) {}
- * }
- * ```
- *
- * will create the following dependency:
- *
- * ```
- * new Dependency(Key.get(AService), [new Exclude()])
- * ```
- *
- * The framework can use `new Exclude()` to handle the `aService` dependency
- * in a specific way.
+ * This is internal to Angular and should not be used directly.
  */
 @CONST()
 export class DependencyMetadata {