[Hotword] Adding pref to track number of times the opt-in popup is shown. Adding functions to the HotwordService and HotwordServiceFactory to find out whether the popup should be shown based on the pref. A test is included for these added functions.

This also fixes some pref accessing bugs in HotwordServiceFactory that were found when writing the test.

Note: The hook up to the extension javascript will occur in a separate CL.

Note: There seem to be two bugs for this so adding this to both for tracking.

BUG=325439,289023
TEST=HotwordServiceTest.ShouldShowOptInPopup

Review URL: https://codereview.chromium.org/136113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246100 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246100
Add Android support in DnsConfigServicePosix.

Add support for Android in DnsConfigServicePosix by:
1. Adding ReadDnsConfig that reads the net.dns[12] system properties.
2. Adding ConfigWatcher that triggers on network change events.
3. Pointing HostsWatcher at /system/etc/hosts.

BUG=149752,334794

Review URL: https://codereview.chromium.org/138623003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246101 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246101