[iOS] ios/web no longer depends on content::BrowserThread.

ios/web/web_thread_impl.h

Index: ios/web/web_thread_impl.h
diff --git a/ios/web/web_thread_impl.h b/ios/web/web_thread_impl.h
index 4ed12fe89152b7d61d2703bca35cbc58d92c7051..7641c61b1d9125f53b264ef4639a801d9b695d99 100644
--- a/ios/web/web_thread_impl.h
+++ b/ios/web/web_thread_impl.h
@@ -10,7 +10,7 @@
 
 namespace web {
 
-class WebThreadDelegate;
+class WebTestSuiteListener;
 
 class WebThreadImpl : public WebThread, public base::Thread {
  public:
@@ -26,20 +26,6 @@ class WebThreadImpl : public WebThread, public base::Thread {
 
   static void ShutdownThreadPool();
 
-  // TODO(stuartmorgan): Move this to WebThread (where it belongs) once
-  // the alternate BrowserThread-backed-WebThread implementation goes away. See
-  // the note in web_thread_delegate.h.
-  //
-  // Sets the delegate for the specified WebThread.
-  //
-  // Only one delegate may be registered at a time. Delegates may be
-  // unregistered by providing a nullptr pointer.
-  //
-  // If the caller unregisters a delegate before CleanUp has been
-  // called, it must perform its own locking to ensure the delegate is
-  // not deleted while unregistering.
-  static void SetDelegate(ID identifier, WebThreadDelegate* delegate);
-
  protected:
   void Init() override;
   void Run(base::MessageLoop* message_loop) override;
@@ -76,6 +62,7 @@ class WebThreadImpl : public WebThread, public base::Thread {
   // For testing.
   friend class TestWebThreadBundle;
   friend class TestWebThreadBundleImpl;
+  friend class WebTestSuiteListener;
   static void FlushThreadPoolHelperForTesting();
 
   // The identifier of this thread.  Only one thread can exist with a given