discardable_memory: Using mojo IPC to replace Chrome IPC

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index c87ed7b42d65bcc9b5232a9551886a98d26100d4..6592c4fba59573958d15541824cbac57482b7420 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -632,11 +632,16 @@ void BrowserMainLoop::PostMainMessageLoopStart() {
     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_)