Hosting the discardable memory service in the mus process

ui/views/mus/mus_client.cc

Index: ui/views/mus/mus_client.cc
diff --git a/ui/views/mus/mus_client.cc b/ui/views/mus/mus_client.cc
index 93b437ed81f00f1888b8102e2a0290c9ad76d3fa..e641d31482f4301401172507a6135688414119b3 100644
--- a/ui/views/mus/mus_client.cc
+++ b/ui/views/mus/mus_client.cc
@@ -6,10 +6,13 @@
 
 #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 "services/service_manager/public/cpp/connection.h"
 #include "services/service_manager/public/cpp/connector.h"
 #include "services/ui/public/cpp/gpu/gpu_service.h"
 #include "services/ui/public/cpp/property_type_converters.h"
+#include "services/ui/public/interfaces/constants.mojom.h"
 #include "services/ui/public/interfaces/event_matcher.mojom.h"
 #include "services/ui/public/interfaces/window_manager.mojom.h"
 #include "ui/aura/env.h"
@@ -174,11 +177,29 @@ MusClient::MusClient(service_manager::Connector* connector,
     : identity_(identity) {
   DCHECK(!instance_);
   instance_ = this;
+
+  if (!io_task_runner) {

[dcheng, 2016/12/16 09:13:01]

Random thought: I looked through all the callsites I could find in codesearch...
and no one ever passes an IO task runner. Kind of feels like the argument should
just be removed...

(I'm generally not a fan of optional arguments if we don't need them)

[Peng, 2016/12/16 15:03:10]

Good suggestion. I will make a separate CL for it. 

+    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();
+  }
+
   // TODO(msw): Avoid this... use some default value? Allow clients to extend?
   property_converter_ = base::MakeUnique<aura::PropertyConverter>();
 
   wm_state_ = base::MakeUnique<wm::WMState>();
 
+  discardable_memory::mojom::DiscardableSharedMemoryManagerPtr manager_ptr;
+  connector->ConnectToInterface(ui::mojom::kServiceName, &manager_ptr);
+
+  discardable_shared_memory_manager_ = base::MakeUnique<
+      discardable_memory::ClientDiscardableSharedMemoryManager>(
+      std::move(manager_ptr), io_task_runner);
+  base::DiscardableMemoryAllocator::SetInstance(
+      discardable_shared_memory_manager_.get());
+
   gpu_service_ = ui::GpuService::Create(connector, std::move(io_task_runner));
   compositor_context_factory_ =
       base::MakeUnique<aura::MusContextFactory>(gpu_service_.get());