Setup DiscardableMemory in the ash process

ui/aura/mus/window_tree_client.cc

Index: ui/aura/mus/window_tree_client.cc
diff --git a/ui/aura/mus/window_tree_client.cc b/ui/aura/mus/window_tree_client.cc
index bc00034df1b57ced12c7b4e8cd97573612256d7d..1b57f14f5b129b8f4b0614063a38f6bc6f5b712f 100644
--- a/ui/aura/mus/window_tree_client.cc
+++ b/ui/aura/mus/window_tree_client.cc
@@ -13,6 +13,8 @@
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
+#include "base/threading/thread.h"
+#include "components/discardable_memory/client/client_discardable_shared_memory_manager.h"
 #include "mojo/public/cpp/bindings/map.h"
 #include "services/service_manager/public/cpp/connector.h"
 #include "services/ui/common/accelerator_util.h"
@@ -173,7 +175,8 @@ WindowTreeClient::WindowTreeClient(
     WindowTreeClientDelegate* delegate,
     WindowManagerDelegate* window_manager_delegate,
     mojo::InterfaceRequest<ui::mojom::WindowTreeClient> request,
-    scoped_refptr<base::SingleThreadTaskRunner> io_task_runner)
+    scoped_refptr<base::SingleThreadTaskRunner> io_task_runner,
+    bool create_discardable_memory)
     : connector_(connector),
       client_id_(0),
       next_window_id_(1),
@@ -192,17 +195,42 @@ WindowTreeClient::WindowTreeClient(
   if (window_manager_delegate)
     window_manager_delegate->SetWindowManagerClient(this);
   if (connector) {  // |connector| can be null in tests.
-    gpu_ = ui::Gpu::Create(connector, std::move(io_task_runner));
+    if (!io_task_runner) {
+      // |io_task_runner| is null in most case. But for the browser process,
+      // the |io_task_runner| is the browser's IO thread.
+      io_thread_ = base::MakeUnique<base::Thread>("IOThread");
+      base::Thread::Options thread_options(base::MessageLoop::TYPE_IO, 0);
+      thread_options.priority = base::ThreadPriority::NORMAL;
+      CHECK(io_thread_->StartWithOptions(thread_options));
+      io_task_runner = io_thread_->task_runner();
+    }
+
+    gpu_ = ui::Gpu::Create(connector, io_task_runner);
     compositor_context_factory_ =
         base::MakeUnique<MusContextFactory>(gpu_.get());
     initial_context_factory_ = Env::GetInstance()->context_factory();
     Env::GetInstance()->set_context_factory(compositor_context_factory_.get());
+
+    // WindowServerTest will create more than one WindowTreeClient. We will not
+    // create the discardable memory manager for those tests.
+    if (create_discardable_memory) {
+      discardable_memory::mojom::DiscardableSharedMemoryManagerPtr manager_ptr;
+      connector->BindInterface(ui::mojom::kServiceName, &manager_ptr);
+      discardable_shared_memory_manager_ = base::MakeUnique<
+          discardable_memory::ClientDiscardableSharedMemoryManager>(
+          std::move(manager_ptr), std::move(io_task_runner));
+      base::DiscardableMemoryAllocator::SetInstance(
+          discardable_shared_memory_manager_.get());
+    }
   }
 }
 
 WindowTreeClient::~WindowTreeClient() {
   in_destructor_ = true;
 
+  if (discardable_shared_memory_manager_)
+    base::DiscardableMemoryAllocator::SetInstance(nullptr);
+
   for (WindowTreeClientObserver& observer : observers_)
     observer.OnWillDestroyClient(this);