Remove MessageLoop references in /ios/web

MessageLoop is going away soon.

This CL was uploaded by git cl split.

R=eugenebut@chromium.org

Bug: 891670
Change-Id: I444463f03ff009d296f846a459b3bc6f6fdc1038
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1946227
Auto-Submit: Carlos Caballero <carlscab@google.com>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#720858}

ios/web/test/test_web_thread.cc

@@ -5,7 +5,6 @@
 #include "ios/web/public/test/test_web_thread.h"
 
 #include "base/macros.h"
-#include "base/message_loop/message_loop.h"
 #include "base/message_loop/message_pump_type.h"
 #include "ios/web/web_sub_thread.h"
 #include "ios/web/web_thread_impl.h"
@@ -24,10 +23,6 @@ TestWebThread::TestWebThread(
     : identifier_(identifier),
       fake_thread_(new WebThreadImpl(identifier_, thread_runner)) {}
 
-TestWebThread::TestWebThread(WebThread::ID identifier,
-                             base::MessageLoop* message_loop)
-    : TestWebThread(identifier, message_loop->task_runner()) {}
-
 TestWebThread::~TestWebThread() {
   // The upcoming WebThreadImpl::ResetGlobalsForTesting() call requires that
   // |identifier_| completed its shutdown phase.