Move WebAXObjectProxy and AccessibleController from CppBoundClass to gin::Wrappable

BUG=297480, 331301

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=253821

Review URL: https://codereview.chromium.org/172263002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254432 0039d316-1c4b-4281-b951-d872f2087c98
Linux Sandbox: add Credentials::SupportsNewUserNS()

We need to be able to check for unprivileged namespace support without
actually unsharing the current namespace.

We add a method that creates a new process with a new user namespace and
see if this succeeds.

BUG=312380
NOTRY=true

Review URL: https://codereview.chromium.org/182453004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254433 0039d316-1c4b-4281-b951-d872f2087c98
Handle waitpid returning EINTR.

Review URL: https://codereview.chromium.org/184963002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254434 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254433
Removal of drag window to user tray icon functionality

BUG=348133
TEST=let it run and compiled - removal of code

Review URL: https://codereview.chromium.org/184113005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254435 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254435