Cast: IPC from browser to renderer to send packet events from transport to cast library.

- Added a new IPC message: CastMsg_RawEvents
- Transmit cast logging settings to transport on browser side by adding a new field in CastTransportConfig.
- Install a LoggingImpl on transport side
-- If raw event logging is enabled, install a SimpleEventSubscriber to capture packet events.
-- If raw event logging is enabled, a RepeatingTimer will   be started to call the subscriber to collect packet events and send back to cast library via the IPC.

NOTE: Currently, no actual packet events are logged on the transport. That will be in the next CL. There are two ways to do this:
- Pass LoggingImpl to sub components on the transport (paced_sender, rtp_packetizer, etc.)
- Pass a callback that will be propagated down and invoked at the right place.

BUG=343992

Review URL: https://codereview.chromium.org/178073004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255579 0039d316-1c4b-4281-b951-d872f2087c98
Pre-emptively add an (unused) #define for record-time filter scaling.

This will be used in Blink to protect the old implementation of hiDPI
filter scaling. Once CC has been taught how to apply hiDPI to filters,
the Blink implementation will be switched off at the same time by
removing this #define.

BUG=281516

Review URL: https://codereview.chromium.org/182863007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255580 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255580