Experiment with redirecting all BrowserThreads (but UI/IO) to TaskScheduler

chrome/browser/chrome_content_browser_client.cc

 // 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.
 
 #include "chrome/browser/chrome_content_browser_client.h"
 
 #include <map>
 #include <set>
 #include <utility>
 #include <vector>
@@ skipping 3271 matching lines @@
                                       arraysize(kWebRtcDevSwitchNames));
   }
 }
 #endif  // BUILDFLAG(ENABLE_WEBRTC)
 
 std::unique_ptr<content::MemoryCoordinatorDelegate>
 ChromeContentBrowserClient::GetMemoryCoordinatorDelegate() {
   return memory::ChromeMemoryCoordinatorDelegate::Create();
 }
 
+bool ChromeContentBrowserClient::
+    RedirectNonUINonIOBrowserThreadsToTaskScheduler() {
+  return variations::GetVariationParamValue(
+             "BrowserScheduler", "RedirectNonUINonIOBrowserThreads") == "true";
+}
+
 #if BUILDFLAG(ENABLE_MEDIA_REMOTING)
 void ChromeContentBrowserClient::CreateMediaRemoter(
     content::RenderFrameHost* render_frame_host,
     media::mojom::RemotingSourcePtr source,
     media::mojom::RemoterRequest request) {
 #if defined(ENABLE_MEDIA_ROUTER)
   CastRemotingConnector::CreateMediaRemoter(
       render_frame_host, std::move(source), std::move(request));
 #else
   // Chrome's media remoting implementation depends on the Media Router
   // infrastructure to identify remote sinks and provide the user interface for
   // sink selection. In the case where the Media Router is not present, simply
   // drop the interface request. This will prevent code paths for media remoting
   // in the renderer process from activating.
 #endif
 }
 #endif  // BUILDFLAG(ENABLE_MEDIA_REMOTING)