Improve unprefixed MediaSource test coverage.

LayoutTests/http/tests/media/media-source/mediasource-addsourcebuffer.html

Index: LayoutTests/http/tests/media/media-source/mediasource-addsourcebuffer.html
diff --git a/LayoutTests/http/tests/media/media-source/mediasource-addsourcebuffer.html b/LayoutTests/http/tests/media/media-source/mediasource-addsourcebuffer.html
index 50134beb7b3d6a4b9291c638432cf2b464b356b2..523a005d269f2362fbc0ea4e5f2a4f40383649f4 100644
--- a/LayoutTests/http/tests/media/media-source/mediasource-addsourcebuffer.html
+++ b/LayoutTests/http/tests/media/media-source/mediasource-addsourcebuffer.html
@@ -12,6 +12,15 @@
         <script>
           mediasource_test(function(test, mediaElement, mediaSource)
           {
+              mediaSource.endOfStream();
+              assert_throws("InvalidStateError",
+                          function() { mediaSource.addSourceBuffer(MediaSourceUtil.AUDIO_VIDEO_TYPE); },
+                          "addSourceBuffer() threw an exception when in 'ended' state.");
+              test.done();
+          }, "Test addSourceBuffer() in 'ended' state.");
+
+          mediasource_test(function(test, mediaElement, mediaSource)
+          {
               assert_throws("InvalidAccessError",
                           function() { mediaSource.addSourceBuffer(""); },
                           "addSourceBuffer() threw an exception when passed an empty string.");
@@ -26,7 +35,6 @@
               test.done();
           }, "Test addSourceBuffer() with unsupported type");
 
-
           mediasource_test(function(test, mediaElement, mediaSource)
           {
               var mimetype = 'video/webm;codecs="vp8,vorbis"';
@@ -86,6 +94,25 @@
               assert_equals(mediaSource.activeSourceBuffers[1], sourceBufferB, "sourceBufferB is in mediaSource.activeSourceBuffers");
               test.done();
           }, "Test addSourceBuffer() with AAC and H.264 in separate SourceBuffers");
+
+          mediasource_test(function(test, mediaElement, mediaSource)
+          {
+              var reachedLimit = false;
+
+             // The 20 here is an arbitrary upper limit to make sure the test terminates. This test
+             // assumes that implementations won't support more than 20 SourceBuffers simultaneously.
+             for (var i = 0; i < 20; ++i) {
+                 try {
+                     mediaSource.addSourceBuffer(MediaSourceUtil.AUDIO_VIDEO_TYPE);
+                 } catch(e) {
+                     assert_equals(e.name, "QuotaExceededError");
+                     reachedLimit = true;
+                     break;
+                 }
+             }
+             assert_true(reachedLimit, "Reached SourceBuffer limit.");
+             test.done();
+          }, "Test addSourceBuffer() QuotaExceededError.");
         </script>
     </body>
 </html>