Add DesktopCapturer::Result::MAX_VALUE

MAX_VALUE will be used in chromoting_messages.h to define range of
valid DesktopCapturer::Result values.

BUG=webrtc:5950
R=jamiewalch@chromium.org

Review URL: https://codereview.webrtc.org/2069103003 .

Cr-Original-Commit-Position: refs/heads/master@{#13157}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 4c17abe35e0ffaea71dd3c2f5f67c3ddf49a6ef3
1 file changed