Remove all remaining deprecated Web/BrowserThreads!!

(except BrowserThread::FILE which has a handful use cases left still and
will follow suit shortly)

(BrowserThread::PROCESS_LAUNCHER migration was put on hold because of
Android specific requirements around process launching)

Remaining usage of TestBrowserThreadBundle::REAL_DB_THREAD could simply
be removed as all of the product code was already migrated to TaskScheduler
which always uses real threads in unit tests.

Bug: 689520, 365909, 752144
Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester
Change-Id: Id70b722aa35e8568795d5aac16947392ac1597be

NOPRESUBMIT=True (for content/browser/browser_thread_impl.cc:211)

Change-Id: Id70b722aa35e8568795d5aac16947392ac1597be
Reviewed-on: https://chromium-review.googlesource.com/610880
Reviewed-by: Alexei Svitkine <[email protected]>
Reviewed-by: John Abd-El-Malek <[email protected]>
Reviewed-by: Dirk Pranke <[email protected]>
Reviewed-by: Sylvain Defresne <[email protected]>
Commit-Queue: Gabriel Charette <[email protected]>
Cr-Commit-Position: refs/heads/master@{#503732}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 4774d18..24c1c64 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -343,7 +343,7 @@
       (),
     ),
     (
-      r'/(WebThread|BrowserThread)::(FILE|FILE_USER_BLOCKING|DB|CACHE)',
+      'BrowserThread::FILE',
       (
         'The non-UI/IO BrowserThreads are deprecated, please migrate this',
         'code to TaskScheduler. See https://goo.gl/mDSxKl for details.',