drive: orphan json gdoc files is shared instead of being copied.

This is partly for changing the gdoc copy behavior and is partly
for preparing cross-profile sharing in multi-profile-enabled Files.app.

BUG=350776

Review URL: https://codereview.chromium.org/198333005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257064 0039d316-1c4b-4281-b951-d872f2087c98
Revert 257022 "Implement wallpaper policy"

This leads to a crash on the IO thread in CheckPolicyIndicators_12 on Chrome OS:

http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%282%29/builds/22314
http://build.chromium.org/p/chromium.memory/builders/Linux%20Chromium%20OS%20ASan%2BLSan%20Tests%20%281%29/builds/263

> Implement wallpaper policy
> 
> BUG=220418
> R=bshe@chromium.org (for ash_user_wallpaper_delegate.cc)
> R=nkostylev@chromium.org (for chrome/browser/chromeos/login/*)
> R=bartfab@chromium.org (for configuration_policy_handler_list_factory.cc)
> R=jhawkins@chromium.org (for chrome/browser/resources/options/browser_options_handler.{cc,h})
> R=dconnelly@chromium.org (for policy_template.json)
> R=asvitkine@chromium.org (for histograms.xml)
> 
> Review URL: https://codereview.chromium.org/184223004

TBR=tnagel@chromium.org

Review URL: https://codereview.chromium.org/200083003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257065 0039d316-1c4b-4281-b951-d872f2087c98
Ask whether to end session when last window is closed in public session

A user closing all browser and app windows may either be a power user
cleaning up or a user less familiar with Chrome OS trying to exit the
browser (and thus, the session). Since we do not know which one is the
case, show a dialog that asks the user whether to exit the session when
the last window is closed.

BUG=278247
TEST=New browser test
R=derat@chromium.org, stevenjb@chromium.org

Review URL: https://codereview.chromium.org/197333002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257066 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 257066
Move clients of BrowserContextKeyedService to use KeyedService (#4)

This change covers:
- //components
- Roughly half of the remaining clients in //chrome

BUG=351704
TBR=jochen

Review URL: https://codereview.chromium.org/198193002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257067 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 257067