viz: Convert a sync api in ServerGpuMemoryBufferManager into async.

components/viz/common/server_gpu_memory_buffer_manager.h

Index: components/viz/common/server_gpu_memory_buffer_manager.h
diff --git a/components/viz/common/server_gpu_memory_buffer_manager.h b/components/viz/common/server_gpu_memory_buffer_manager.h
index c34eda825d3ec8e20583999d874e6aa90c1ad15e..f546bc76f9cbf1b5a400a656675188b829320c82 100644
--- a/components/viz/common/server_gpu_memory_buffer_manager.h
+++ b/components/viz/common/server_gpu_memory_buffer_manager.h
@@ -9,7 +9,8 @@
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
-#include "base/threading/thread_checker.h"
+#include "base/sequenced_task_runner.h"
+#include "base/synchronization/waitable_event.h"
 #include "gpu/command_buffer/client/gpu_memory_buffer_manager.h"
 #include "gpu/ipc/host/gpu_memory_buffer_support.h"
 
@@ -23,8 +24,9 @@ namespace viz {
 
 // This GpuMemoryBufferManager implementation is for [de]allocating gpu memory
 // from the gpu process over the mojom.GpuService api.
-class ServerGpuMemoryBufferManager : public gpu::GpuMemoryBufferManager,
-                                     public base::ThreadChecker {
+// Note that |CreateGpuMemoryBuffer()| can be called on any thread. All the rest
+// of the functions must be called on the thread this object is created on.
+class ServerGpuMemoryBufferManager : public gpu::GpuMemoryBufferManager {
  public:
   ServerGpuMemoryBufferManager(ui::mojom::GpuService* gpu_service,
                                int client_id);
@@ -36,13 +38,14 @@ class ServerGpuMemoryBufferManager : public gpu::GpuMemoryBufferManager,
 
   void DestroyAllGpuMemoryBufferForClient(int client_id);
 
-  gfx::GpuMemoryBufferHandle CreateGpuMemoryBufferHandle(
+  void AllocateGpuMemoryBuffer(
       gfx::GpuMemoryBufferId id,
       int client_id,
       const gfx::Size& size,
       gfx::BufferFormat format,
       gfx::BufferUsage usage,
-      gpu::SurfaceHandle surface_handle);
+      gpu::SurfaceHandle surface_handle,
+      base::OnceCallback<void(const gfx::GpuMemoryBufferHandle&)> callback);
 
   // Overridden from gpu::GpuMemoryBufferManager:
   std::unique_ptr<gfx::GpuMemoryBuffer> CreateGpuMemoryBuffer(
@@ -54,6 +57,11 @@ class ServerGpuMemoryBufferManager : public gpu::GpuMemoryBufferManager,
                                const gpu::SyncToken& sync_token) override;
 
  private:
+  void OnGpuMemoryBufferAllocated(
+      int client_id,
+      base::OnceCallback<void(const gfx::GpuMemoryBufferHandle&)> callback,
+      const gfx::GpuMemoryBufferHandle& handle);
+
   ui::mojom::GpuService* gpu_service_;
   const int client_id_;
   int next_gpu_memory_id_ = 1;
@@ -62,8 +70,10 @@ class ServerGpuMemoryBufferManager : public gpu::GpuMemoryBufferManager,
       std::unordered_set<gfx::GpuMemoryBufferId,
                          BASE_HASH_NAMESPACE::hash<gfx::GpuMemoryBufferId>>;
   std::unordered_map<int, NativeBuffers> native_buffers_;
+  std::unordered_set<int> pending_buffers_;
 
   const gpu::GpuMemoryBufferConfigurationSet native_configurations_;
+  scoped_refptr<base::SequencedTaskRunner> task_runner_;
   base::WeakPtrFactory<ServerGpuMemoryBufferManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ServerGpuMemoryBufferManager);