diff --git a/closure/goog/disposable/idisposable.js b/closure/goog/disposable/idisposable.js
index <HASH>..<HASH> 100644
--- a/closure/goog/disposable/idisposable.js
+++ b/closure/goog/disposable/idisposable.js
@@ -36,10 +36,10 @@ goog.disposable.IDisposable = function() {};
  * Disposes of the object and its resources.
  * @return {void} Nothing.
  */
-goog.disposable.IDisposable.prototype.dispose;
+goog.disposable.IDisposable.prototype.dispose = goog.abstractMethod;
 
 
 /**
  * @return {boolean} Whether the object has been disposed of.
  */
-goog.disposable.IDisposable.prototype.isDisposed;
+goog.disposable.IDisposable.prototype.isDisposed = goog.abstractMethod;
Add goog.abstractMethod to goog.disposable.IDisposable methods. This will make it easier to mock in unit tests.
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Created by MOE: <URL>