Check adaptive playback support via CodecCapabilities

Check adaptive playback support via CodecCapabilities

Added flags field to CodecCapabilities, so that applications
can query whether codecs support various features.  For now
added one video-decoder feature:

kFlagSupportsAdaptivePlayback

Media playback applications can query it to see if a codec
supports seamless resolution changes, such as by supporting
dynamic output buffers.

Signed-off-by: Lajos Molnar <lajos@google.com>
Change-Id: I09da46e8ab6b8645fa2749e33128e49eda2e865b
Related-to-bug: 7093648