Rename fast/ime tests so it matches the current method/interface names

BUG=none
TEST=layouttest fast/ime

Review URL: https://chromiumcodereview.appspot.com/23498017

git-svn-id: svn://svn.chromium.org/blink/trunk@157482 bbb929c8-8fbe-4397-9dbb-9b2b20218538