Adding a few new MSE tests based on the spec.

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 523a005d269f2362fbc0ea4e5f2a4f40383649f4..fd9c403f06c4da702a06d34e435f8ec5c7d427b6 100644
--- a/LayoutTests/http/tests/media/media-source/mediasource-addsourcebuffer.html
+++ b/LayoutTests/http/tests/media/media-source/mediasource-addsourcebuffer.html
@@ -26,7 +26,15 @@
                           "addSourceBuffer() threw an exception when passed an empty string.");
               test.done();
           }, "Test addSourceBuffer() with empty type");
-
+          
+          mediasource_test(function(test, mediaElement, mediaSource)
+          {
+              assert_throws("NotSupportedError",
+                          function() { mediaSource.addSourceBuffer(null); },
+                          "addSourceBuffer() threw an exception when passed null.");
+              test.done();
+          }, "Test addSourceBuffer() with null");
+          
           mediasource_test(function(test, mediaElement, mediaSource)
           {
               assert_throws("NotSupportedError",
@@ -47,7 +55,7 @@
               assert_equals(mediaSource.activeSourceBuffers[0], sourceBuffer, "SourceBuffer is in mediaSource.activeSourceBuffers");
               test.done();
           }, "Test addSourceBuffer() with Vorbis and VP8");
-
+        
           mediasource_test(function(test, mediaElement, mediaSource)
           {
               var videoMimetype = 'video/webm;codecs="vp8"';
@@ -67,6 +75,32 @@
 
           mediasource_test(function(test, mediaElement, mediaSource)
           {
+              var mimetype = MediaSourceUtil.VIDEO_ONLY_TYPE;
+
+              assert_true(MediaSource.isTypeSupported(mimetype), mimetype + " is supported");
+
+              var sourceBuffer = mediaSource.addSourceBuffer(mimetype);
+              assert_true(sourceBuffer != null, "New SourceBuffer returned");
+              assert_equals(mediaSource.sourceBuffers[0], sourceBuffer, "SourceBuffer is in mediaSource.sourceBuffers");
+              assert_equals(mediaSource.activeSourceBuffers[0], sourceBuffer, "SourceBuffer is in mediaSource.activeSourceBuffers");
+              test.done();
+          }, "Test addSourceBuffer() video only");
+          
+          mediasource_test(function(test, mediaElement, mediaSource)
+          {
+              var mimetype = MediaSourceUtil.AUDIO_ONLY_TYPE;
+
+              assert_true(MediaSource.isTypeSupported(mimetype), mimetype + " is supported");
+
+              var sourceBuffer = mediaSource.addSourceBuffer(mimetype);
+              assert_true(sourceBuffer != null, "New SourceBuffer returned");
+              assert_equals(mediaSource.sourceBuffers[0], sourceBuffer, "SourceBuffer is in mediaSource.sourceBuffers");
+              assert_equals(mediaSource.activeSourceBuffers[0], sourceBuffer, "SourceBuffer is in mediaSource.activeSourceBuffers");
+              test.done();
+          }, "Test addSourceBuffer() audio only");
+
+          mediasource_test(function(test, mediaElement, mediaSource)
+          {
               var mimetype = 'video/mp4;codecs="avc1.4D4001,mp4a.40.2"';
 
               assert_true(MediaSource.isTypeSupported(mimetype), mimetype + " is supported");