Don't use |session.closed| in DrmEngine.destroy.

If a session has been created but the license request hasn't been sent,
the session is not "callable".  This will cause the |session.close()|
to be rejected and the |session.closed| Promise to never resolve.  So
in DrmEngine.destroy, we should be using the Promise returned from
|session.close()| instead of |session.closed|.  The |session.close()|
Promise will only resolve once the |session.closed| Promise is resolved
so they are effectively the same.

Closes #664

Change-Id: Ia619740d1eb3fa8ca1bdf121574d1efb1ddbea26

lib/media/drm_engine.js

@@ -131,9 +131,7 @@ shaka.media.DrmEngine.prototype.destroy = function() {
     // Ignore any errors when closing the sessions.  One such error would be
     // an invalid state error triggered by closing a session which has not
     // generated any key requests.
-    activeSession.session.close().catch(Functional.noop);
-    goog.asserts.assert(activeSession.session.closed, 'Bad EME implementation');
-    return activeSession.session.closed;
+    return activeSession.session.close().catch(Functional.noop);
   });
   this.allSessionsLoaded_.reject();
 

test/media/drm_engine_unit.js

@@ -1393,6 +1393,39 @@ describe('DrmEngine', function() {
       }).catch(fail).then(done);
       // onError is a failure by default.
     });
+
+    it('still completes if session is not callable', function(done) {
+      // Before, we would use |session.closed| as part of destroy().  However,
+      // this doesn't work if the session is not callable (no license request
+      // sent).  So |session.closed| should never resolve and |session.close()|
+      // should be rejected and destroy() should still succeed.
+      // https://github.com/google/shaka-player/issues/664
+      initAndAttach().then(function() {
+        session1.closed = new shaka.util.PublicPromise();
+        session2.closed = new shaka.util.PublicPromise();
+        session1.close.and.returnValue(Promise.reject());
+        session2.close.and.returnValue(Promise.reject());
+
+        var initData1 = new Uint8Array(1);
+        var initData2 = new Uint8Array(2);
+        mockVideo.on['encrypted'](
+            { initDataType: 'webm', initData: initData1 });
+        mockVideo.on['encrypted'](
+            { initDataType: 'webm', initData: initData2 });
+
+        // Still resolve these since we are mocking close and closed.  This
+        // ensures DrmEngine is in the correct state.
+        var message = new Uint8Array(0);
+        session1.on['message']({ target: session1, message: message });
+        session1.update.and.returnValue(Promise.resolve());
+        session2.on['message']({ target: session2, message: message });
+        session2.update.and.returnValue(Promise.resolve());
+
+        return shaka.test.Util.delay(0.5);
+      }).then(function() {
+        return drmEngine.destroy();
+      }).catch(fail).then(done);
+    });
   });  // describe('destroy')
 
   describe('getDrmInfo', function() {