Short-circuit regex logic in AutocompleteInput::Parse for non-js scheme

The regex is notably more expensive than a simple string comparison, and
isn't necessary unless the scheme (which we already know) is javascript,
so we can avoid the expense in most cases.

Local testing on an Android emulator (release build) showed a 4x speedup
for Parse(), improving from 0.2ms average to 0.05ms. This adds up to a
full ms of delay when loading a url, since we call parse() five times
while generating the url bar data.

Bug: none
Change-Id: I6427e7b2a4ddbd9e4c362707df659d776e66e743
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3923871
Reviewed-by: Travis Skare <skare@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Patrick Noland <pnoland@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1053769}