gyp: Disable media recording unittests on ChromeCast

content/content_tests.gypi

Index: content/content_tests.gypi
diff --git a/content/content_tests.gypi b/content/content_tests.gypi
index ae660cc64941db59537dd643401a263fd6f19d4b..b41f55a3f09079ef7ced8727739b1329de97b4fb 100644
--- a/content/content_tests.gypi
+++ b/content/content_tests.gypi
@@ -1282,6 +1282,13 @@
                 '../third_party/libvpx_new/libvpx.gyp:libvpx_new',
               ],
             }],
+            ['chromecast == 1', {
+              'sources!': [
+                'renderer/media/audio_track_recorder_unittest.cc',
+                'renderer/media/media_recorder_handler_unittest.cc',
+                'renderer/media/video_track_recorder_unittest.cc',
+              ],
+            }],
             # Avoid windows due to non-availability of cursor resources in test.
             ['OS != "linux"', {
               'sources!': [