discardable_memory: Using mojo IPC to replace Chrome IPC

content/browser/browser_main_loop.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 "content/browser/browser_main_loop.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 614 matching lines @@
   {
     base::SetRecordActionTaskRunner(
         BrowserThread::GetTaskRunnerForThread(BrowserThread::UI));
   }
 
 #if defined(OS_WIN)
   if (base::win::GetVersion() >= base::win::VERSION_WIN8)
     screen_orientation_delegate_.reset(new ScreenOrientationDelegateWin());
 #endif
 
+  // Initialize the singleton discardable_memory::DiscardableSharedMemoryManager
+  // here to avoid initialization happening in IO thread.
+  auto discardable_shared_memory_manager =
+      discardable_memory::DiscardableSharedMemoryManager::current();

[reveman, 2016/11/18 21:55:25]

Why would it be initialize on the IO thread? Ideally we'd remove
DiscardableSharedMemoryManager::current() and instead pass a pointer to an
instance allocated here to where it's used. That might be complicated so if we
need explicit allocation to happen here then adding a CreateInstance() function
is OK I think.

[Peng, 2016/11/21 15:56:38]

I just tried your suggestion. The content_browsertest crashes. Because the
content_browsertest uses the kSingleProcess flag, and the content_browsertest
needs the child discardable shared memory manager in childthreadimpl.

+
   // TODO(boliu): kSingleProcess check is a temporary workaround for
   // in-process Android WebView. crbug.com/503724 tracks proper fix.
   if (!parsed_command_line_.HasSwitch(switches::kSingleProcess)) {
     base::DiscardableMemoryAllocator::SetInstance(
-        discardable_memory::DiscardableSharedMemoryManager::current());
+        discardable_shared_memory_manager);
   }
 
   if (parts_)
     parts_->PostMainMessageLoopStart();
 
   // Start startup tracing through TracingController's interface. TraceLog has
   // been enabled in content_main_runner where threads are not available. Now We
   // need to start tracing for all other tracing agents, which require threads.
   if (parsed_command_line_.HasSwitch(switches::kTraceStartup)) {
     base::trace_event::TraceConfig trace_config(
@@ skipping 969 matching lines @@
     scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner =
         audio_thread_->task_runner();
     audio_manager_ = media::AudioManager::Create(std::move(audio_task_runner),
                                                  std::move(worker_task_runner),
                                                  MediaInternals::GetInstance());
   }
   CHECK(audio_manager_);
 }
 
 }  // namespace content