Fix flags for Chromecast browser test on internal infrastructure

The media playback test was recently added:
https://codereview.chromium.org/1431193005/

and requires specific switches:
* local file access required to load test media
* cma pipeline explicitly enabled in order to test that
* cast ozone platform enabled in order to test overlay frames

These tests have been failing on internal infrastructure (tot build)
because the switches were only configured in testing/buildbot (for
running on Chromium bots).

BUG=

Review URL: https://codereview.chromium.org/1466633004

Cr-Commit-Position: refs/heads/master@{#361134}

chromecast/BUILD.gn

@@ -108,7 +108,7 @@ cast_test_group("cast_tests") {
       "//chromecast/media:cast_media_unittests",
     ]
 
-    filters += [ "cast_shell_browser_test --no-sandbox --disable-gpu" ]
+    filters += [ "cast_shell_browser_test --no-sandbox --enable-local-file-accesses --enable-cma-media-pipeline --ozone-platform=cast" ]
   }
 
   if (!disable_display) {

chromecast/chromecast_tests.gypi

@@ -180,7 +180,7 @@
           ],
           'variables': {
             'filters': [
-              'cast_shell_browser_test --no-sandbox --disable-gpu',
+              'cast_shell_browser_test --no-sandbox --enable-local-file-accesses --enable-cma-media-pipeline --ozone-platform=cast',
             ],
           },
         }],