Cast Extensions API: Major namespace and object renaming

There is no functional change in this patch. This change only does
renaming.

Extensions API namespaces:
webrtc.castSendTransport -> cast.streaming.rtpStream
webrtc.castUdpTransport -> cast.streaming.udpTransport

Class renaming:
WebRtcNativeHandler -> CastStreamingNativeHandler
CastSendTransport -> CastRtpStream

Tests and related files are also renamed to get rid of the webrtc
label.

BUG=301920

Review URL: https://codereview.chromium.org/90083002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238403 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238403
Add OWNER file in components/nacl/renderer

The code in this directory was moved from chrome/renderer/pepper so
the OWNERS over there are the appropriate folks to review the changes
in the new nacl/renderer directory.

This is part of an effort to componentize NaCl code.

BUG=244791

Review URL: https://codereview.chromium.org/99673002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238404 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238404