Extend content::DesktopMediaID to allow Aura windows as capture sources.

content/content_tests.gypi

Index: content/content_tests.gypi
diff --git a/content/content_tests.gypi b/content/content_tests.gypi
index eed3507ea58c9070daf05f0e052d08ffdc067e09..c498959fcb8f6105f7202d0708f38f18ee66fabb 100644
--- a/content/content_tests.gypi
+++ b/content/content_tests.gypi
@@ -715,7 +715,7 @@
         }],
         ['enable_webrtc==1 and chromeos==1', {
           'sources': [
-            'browser/renderer_host/media/desktop_capture_device_ash_unittest.cc',
+            'browser/renderer_host/media/desktop_capture_device_aura_unittest.cc',
           ],
         }],
         # TODO(jrg): remove the OS=="android" section?