[Telemetry] Use unhandled exception formatter everywhere.

BUG=
NOTRY=True

Review URL: https://codereview.chromium.org/61073003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237012 0039d316-1c4b-4281-b951-d872f2087c98
wpad: do dhcp discovery before trying quickcheck

When we're deciding what state to transition into after a wait or a fetch
failure, consider whether the source we're about to try is DHCP or DNS. If it's
DHCP, skip QuickCheck, since QuickCheck is irrelevant for DHCP sources. Also,
add a new unit test covering this case, and a MockDhcpProxyScriptFetcher class
for testing.

TEST=unit
BUG=320694

Review URL: https://codereview.chromium.org/63373005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237013 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237013
Hide ephemeral apps from UI

Added an IS_EPHEMERAL flag for extensions to identify ephemeral apps.
Ephemeral apps are integrated into the extension system, but we use
the flag to hide them from UI such as the app launcher, NTP and
extension management page.

Garbage collection of unused ephemeral apps will be implemented in a
future patch.

This feature is hidden behind the "enable-ephemeral-apps" switch.

BUG=312460

Review URL: https://codereview.chromium.org/75323003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237014 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237014