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 648873d6c243ff38638dfb43e33d088dd150381f..c6650f59b8ff7df419fe07ba5ea43b6bd8fd393c 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -631,11 +631,16 @@ 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();
+
   // 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_)