[BrowserThread] Remove unused SetIOThreadDelegate method

The last caller was removed in crrev.com/669295.


Bug: 934009
Change-Id: I3cabd207d231c95787ad4511abbf296fa39feebb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1902271
Auto-Submit: Gabriel Charette <gab@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713581}

content/browser/browser_process_sub_thread.cc

@@ -17,7 +17,6 @@
 #include "content/browser/utility_process_host.h"
 #include "content/common/child_process_host_impl.h"
 #include "content/public/browser/browser_child_process_host_iterator.h"
-#include "content/public/browser/browser_thread_delegate.h"
 #include "content/public/common/process_type.h"
 #include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_request.h"
@@ -32,20 +31,6 @@
 
 namespace content {
 
-namespace {
-BrowserThreadDelegate* g_io_thread_delegate = nullptr;
-}  // namespace
-
-// static
-void BrowserThread::SetIOThreadDelegate(BrowserThreadDelegate* delegate) {
-  // |delegate| can only be set/unset while BrowserThread::IO isn't up.
-  DCHECK(!BrowserThread::IsThreadInitialized(BrowserThread::IO));
-  // and it cannot be set twice.
-  DCHECK(!g_io_thread_delegate || !delegate);
-
-  g_io_thread_delegate = delegate;
-}
-
 BrowserProcessSubThread::BrowserProcessSubThread(BrowserThread::ID identifier)
     : base::Thread(BrowserThreadImpl::GetThreadName(identifier)),
       identifier_(identifier) {
@@ -122,9 +107,6 @@ void BrowserProcessSubThread::CleanUp() {
   if (BrowserThread::CurrentlyOn(BrowserThread::IO))
     IOThreadCleanUp();
 
-  if (identifier_ == BrowserThread::IO && g_io_thread_delegate)
-    g_io_thread_delegate->CleanUp();
-
   notification_service_.reset();
 
 #if defined(OS_WIN)
@@ -136,12 +118,6 @@ void BrowserProcessSubThread::CompleteInitializationOnBrowserThread() {
   DCHECK_CALLED_ON_VALID_THREAD(browser_thread_checker_);
 
   notification_service_ = std::make_unique<NotificationServiceImpl>();
-
-  if (identifier_ == BrowserThread::IO && g_io_thread_delegate) {
-    // Allow blocking calls while initializing the IO thread.
-    base::ScopedAllowBlocking allow_blocking_for_init;
-    g_io_thread_delegate->Init();
-  }
 }
 
 // Mark following two functions as NOINLINE so the compiler doesn't merge

content/public/browser/BUILD.gn

@@ -99,7 +99,6 @@ jumbo_source_set("browser_sources") {
     "browser_task_traits.h",
     "browser_thread.cc",
     "browser_thread.h",
-    "browser_thread_delegate.h",
     "browser_url_handler.h",
     "browsing_data_filter_builder.h",
     "browsing_data_remover.h",

content/public/browser/browser_thread.h

@@ -21,7 +21,6 @@
 
 namespace content {
 
-class BrowserThreadDelegate;
 class BrowserThreadImpl;
 
 // Use DCHECK_CURRENTLY_ON(BrowserThread::ID) to assert that a function can only
@@ -121,16 +120,6 @@ class CONTENT_EXPORT BrowserThread {
   // sets identifier to its ID.  Otherwise returns false.
   static bool GetCurrentThreadIdentifier(ID* identifier) WARN_UNUSED_RESULT;
 
-  // Sets the delegate for BrowserThread::IO.
-  //
-  // Only one delegate may be registered at a time. The delegate may be
-  // unregistered by providing a nullptr pointer.
-  //
-  // The delegate can only be registered through this call before
-  // BrowserThreadImpl(BrowserThread::IO) is created and unregistered after
-  // it was destroyed and its underlying thread shutdown.
-  static void SetIOThreadDelegate(BrowserThreadDelegate* delegate);
-
   // Use these templates in conjunction with RefCountedThreadSafe or scoped_ptr
   // when you want to ensure that an object is deleted on a specific thread.
   // This is needed when an object can hop between threads (i.e. UI -> IO ->

content/public/browser/browser_thread_delegate.h

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_DELEGATE_H_
-#define CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_DELEGATE_H_
-
-#include "content/common/content_export.h"
-
-namespace content {
-
-// A Delegate for content embedders to perform extra initialization/cleanup on
-// BrowserThread::IO.
-class BrowserThreadDelegate {
- public:
-  virtual ~BrowserThreadDelegate() = default;
-
-  // Called prior to completing initialization of BrowserThread::IO.
-  virtual void Init() = 0;
-
-  // Called during teardown of BrowserThread::IO.
-  virtual void CleanUp() = 0;
-};
-
-}  // namespace content
-
-#endif  // CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_DELEGATE_H_