Rename ResourceFetcher::requestXxx to ResourceFetcher::fetchXxx

BUG=263277
TEST=none
R=abarth,japhet

Review URL: https://chromiumcodereview.appspot.com/22877011

git-svn-id: svn://svn.chromium.org/blink/trunk@156766 bbb929c8-8fbe-4397-9dbb-9b2b20218538