Remove --hide-scrollbars Flag

This command lien flag is used only by Android Webview, which we now
plump through using another setting mechanism instead.

BUG=350136

Review URL: https://codereview.chromium.org/195783002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256623 0039d316-1c4b-4281-b951-d872f2087c98
Mac AVFoundation: disabled by default;

This CL changes AVFoundation to be disabled by default and flips the flag
(and associated chrome://flags) to "enable-avfoundation". This should
address the performance regressions in the bugs.

This also affects the webrtc apprtc browser test(s), where AVFoundation was
disabled for ManyCam fake webcam to work properly. Same applies to
webrtc browser tests and webrtc quality browser tests.

BUG=288562, 348020, 349616, 342790, 327618

Review URL: https://codereview.chromium.org/189623011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256624 0039d316-1c4b-4281-b951-d872f2087c98
Fix KioskUpdateTest with multi profiles.

BUG=351242

Review URL: https://codereview.chromium.org/196033002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256625 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256625