Comment out the request count check in and re-enable PrerenderPageNewTab.

The logic that prevents a second request from firing currently races, but the
rest of the test is still valuable. See bug.

BUG=335835
TEST=PrerenderBrowserTest.PrerenderPageNewTab,
     PrerenderBrowserTest.PrerenderPageNewTabCrossProcess

Review URL: https://codereview.chromium.org/138163011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246385 0039d316-1c4b-4281-b951-d872f2087c98
Added a BrowserPolicyConnectorIos.

This change also adds a BrowserProcessPlatformPartIos, which is used to create
the a BrowserPolicyConnector of the right type on iOS.

The BrowserPolicyConnector needs a list of policy handlers; this change also
builds the configuration_policy_handler_list_factory on iOS but excludes all
custom policy handlers for now.

BUG=275292

Review URL: https://codereview.chromium.org/140153004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246386 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246386