Moved CCInfobarDelegate tests out of AutofillMetricsTest

The AutofillMetrics unittests will be componentized. The infobar-related tests,
however, cannot be componentized, as infobars are currently a //chrome-level
concept. This CL splits out the infobar-related tests from AutofillMetricsTest
into a new AutofillCCInfobarDelegateTest.

BUG=303083

Review URL: https://codereview.chromium.org/177923004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255842 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255842