Cache Autofill heuristics regexes

Runtime for FormStructureBrowserTest.DataDrivenHeuristics decreased from 2.4s to 1.5s
In particular, the test now spends 61ms in AutofillManager::ParseForms, down from 738ms.

BUG=72242
TEST=unit_tests --gtest_filter=Autofill*:FormStructure*, browser_tests --gtest_filter=Autofill*:FormStructure*

Review URL: http://codereview.chromium.org/7066043

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@87710 0039d316-1c4b-4281-b951-d872f2087c98
8 files changed