Make CanPlayType return "probably" for HI10P h264 videos.

media/test/data/test_key_system_instantiation.html

Index: media/test/data/test_key_system_instantiation.html
diff --git a/media/test/data/test_key_system_instantiation.html b/media/test/data/test_key_system_instantiation.html
index 93e48694ebad89c69823b2aca38777e51daba239..489a3dba4ad706a16d3138ba1f03aefbeaa999e2 100644
--- a/media/test/data/test_key_system_instantiation.html
+++ b/media/test/data/test_key_system_instantiation.html
@@ -4,7 +4,14 @@
       // Since promises run asynchronously, use the pages title to keep track
       // of the result.
       function setResultInTitle(title) {
-        document.title = title;
+        if (title == "" || title == "success" ||
+            title == "Unsupported keySystem" ||
+            title == "None of the requested configurations were supported.") {
+          document.title = title;
+        } else {
+          console.log("Result: " + title);
+          document.title = "failure";

[ddorwin, 2016/03/31 22:31:12]

I believe the title watcher only checks the start of the string, so we can do
"failure: unexpected result '" + title + "'";

+jrummell

[hubbe, 2016/04/01 00:20:59]

It does not:
https://code.google.com/p/chromium/codesearch#chromium/src/content/public/tes...

[ddorwin, 2016/04/01 00:36:42]

Hmm. We had one test where something like that was a problem.
Maybe we should use "unexpected result" or something to be more accurate and
searchable.

[jrummell, 2016/04/01 00:52:52]

I think if the title is not matched completely the TitleWatcher doesn't
recognize it and the test will eventually time out.

[hubbe, 2016/04/04 22:01:49]

Yep, that is exactly what happens.

[hubbe, 2016/04/04 22:01:49]

Sounds like a good idea, done.

+        }
       };
 
       // Compares 2 arrays of MediaKeySystemMediaCapability, comparing only