cast: Support for low-latency interactive mode

media/base/video_frame_metadata.h

Index: media/base/video_frame_metadata.h
diff --git a/media/base/video_frame_metadata.h b/media/base/video_frame_metadata.h
index 48fe509719fc9e3f724086903af85a7845b709cf..bf05ef73916cfcdf21d0023e5828c484406e96a0 100644
--- a/media/base/video_frame_metadata.h
+++ b/media/base/video_frame_metadata.h
@@ -5,6 +5,8 @@
 #ifndef MEDIA_BASE_VIDEO_FRAME_METADATA_H_
 #define MEDIA_BASE_VIDEO_FRAME_METADATA_H_
 
+#include <string>
+
 #include "base/compiler_specific.h"
 #include "base/time/time.h"
 #include "base/values.h"
@@ -77,6 +79,14 @@ class MEDIA_EXPORT VideoFrameMetadata {
     // measurements would be used as feedback.
     RESOURCE_UTILIZATION,
 
+    // This is a boolean that signals that the video capture engine detects
+    // interactive content. One possible optimization that this signal can help
+    // with is adjusting end-to-end latency based on whether the mode is turned

[miu, 2015/12/03 21:26:23]

For a bit more clarity for those unfamiliar with mirroring concepts:

s/with is adjusting/with is remoting content: adjusting/

and

s/based on whether the mode is turned on or off/down to help the user better
coordinate their actions/

[Irfan, 2015/12/04 22:45:37]

Done.

+    // on or off.
+    //
+    // Use Get/SetBoolean for this key.
+    INTERACTIVE_MODE,

[miu, 2015/12/03 21:26:23]

1. naming nit: How about INTERACTIVE_CONTENT?  (i.e., focus is on this
VideoFrame's media content, not an overall systemic "mode")

2. Please move this up so it's in alphabetical order.

[Irfan, 2015/12/04 22:45:37]

Done.

+
     NUM_KEYS
   };