[Impeller] Add implementations for concurrent work-queues.

ci/licenses_golden/licenses_flutter

@@ -450,6 +450,8 @@ FILE: ../../../flutter/impeller/base/base_unittests.cc
 FILE: ../../../flutter/impeller/base/comparable.cc
 FILE: ../../../flutter/impeller/base/comparable.h
 FILE: ../../../flutter/impeller/base/config.h
+FILE: ../../../flutter/impeller/base/platform/darwin/work_queue_darwin.cc
+FILE: ../../../flutter/impeller/base/platform/darwin/work_queue_darwin.h
 FILE: ../../../flutter/impeller/base/promise.cc
 FILE: ../../../flutter/impeller/base/promise.h
 FILE: ../../../flutter/impeller/base/strings.cc
@@ -462,6 +464,10 @@ FILE: ../../../flutter/impeller/base/validation.cc
 FILE: ../../../flutter/impeller/base/validation.h
 FILE: ../../../flutter/impeller/base/version.cc
 FILE: ../../../flutter/impeller/base/version.h
+FILE: ../../../flutter/impeller/base/work_queue.cc
+FILE: ../../../flutter/impeller/base/work_queue.h
+FILE: ../../../flutter/impeller/base/work_queue_common.cc
+FILE: ../../../flutter/impeller/base/work_queue_common.h
 FILE: ../../../flutter/impeller/blobcat/blob.cc
 FILE: ../../../flutter/impeller/blobcat/blob.h
 FILE: ../../../flutter/impeller/blobcat/blob_library.cc

impeller/base/BUILD.gn

@@ -24,8 +24,19 @@ impeller_component("base") {
     "validation.h",
     "version.cc",
     "version.h",
+    "work_queue.cc",
+    "work_queue.h",
+    "work_queue_common.cc",
+    "work_queue_common.h",
   ]
 
+  if (is_ios || is_mac) {
+    sources += [
+      "platform/darwin/work_queue_darwin.cc",
+      "platform/darwin/work_queue_darwin.h",
+    ]
+  }
+
   deps = [ "//flutter/fml" ]
 }
 

impeller/base/platform/darwin/work_queue_darwin.cc

@@ -0,0 +1,38 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "impeller/base/platform/darwin/work_queue_darwin.h"
+
+namespace impeller {
+
+std::shared_ptr<WorkQueueDarwin> WorkQueueDarwin::Create() {
+  auto queue = std::shared_ptr<WorkQueueDarwin>(new WorkQueueDarwin());
+  if (!queue->IsValid()) {
+    return nullptr;
+  }
+  return queue;
+}
+
+WorkQueueDarwin::WorkQueueDarwin()
+    : queue_(::dispatch_queue_create(
+          "io.flutter.impeller.wq",
+          ::dispatch_queue_attr_make_with_qos_class(
+              DISPATCH_QUEUE_CONCURRENT_WITH_AUTORELEASE_POOL,
+              QOS_CLASS_USER_INITIATED,
+              -1))) {}
+
+WorkQueueDarwin::~WorkQueueDarwin() = default;
+
+bool WorkQueueDarwin::IsValid() const {
+  return queue_ != NULL;
+}
+
+// |WorkQueue|
+void WorkQueueDarwin::PostTask(fml::closure task) {
+  dispatch_async(queue_, ^() {
+    task();
+  });
+}
+
+}  // namespace impeller

impeller/base/platform/darwin/work_queue_darwin.h

@@ -0,0 +1,36 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#pragma once
+
+#include <dispatch/dispatch.h>
+
+#include <memory>
+
+#include "flutter/fml/macros.h"
+#include "impeller/base/work_queue.h"
+
+namespace impeller {
+
+class WorkQueueDarwin final : public WorkQueue {
+ public:
+  static std::shared_ptr<WorkQueueDarwin> Create();
+
+  // |WorkQueue|
+  ~WorkQueueDarwin();
+
+  bool IsValid() const;
+
+ private:
+  dispatch_queue_t queue_ = NULL;
+
+  WorkQueueDarwin();
+
+  // |WorkQueue|
+  void PostTask(fml::closure task) override;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(WorkQueueDarwin);
+};
+
+}  // namespace impeller

impeller/base/work_queue.cc

@@ -0,0 +1,13 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/impeller/base/work_queue.h"
+
+namespace impeller {
+
+WorkQueue::WorkQueue() = default;
+
+WorkQueue::~WorkQueue() = default;
+
+}  // namespace impeller

impeller/base/work_queue.h

@@ -0,0 +1,27 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#pragma once
+
+#include <memory>
+
+#include "flutter/fml/closure.h"
+#include "flutter/fml/macros.h"
+
+namespace impeller {
+
+class WorkQueue : public std::enable_shared_from_this<WorkQueue> {
+ public:
+  virtual ~WorkQueue();
+
+  virtual void PostTask(fml::closure task) = 0;
+
+ protected:
+  WorkQueue();
+
+ private:
+  FML_DISALLOW_COPY_AND_ASSIGN(WorkQueue);
+};
+
+}  // namespace impeller

impeller/base/work_queue_common.cc

@@ -0,0 +1,25 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "impeller/base/work_queue_common.h"
+
+namespace impeller {
+
+std::shared_ptr<WorkQueueCommon> WorkQueueCommon::Create() {
+  return std::shared_ptr<WorkQueueCommon>(new WorkQueueCommon());
+}
+
+WorkQueueCommon::WorkQueueCommon()
+    : loop_(fml::ConcurrentMessageLoop::Create(2u)) {}
+
+WorkQueueCommon::~WorkQueueCommon() {
+  loop_->Terminate();
+}
+
+// |WorkQueue|
+void WorkQueueCommon::PostTask(fml::closure task) {
+  loop_->GetTaskRunner()->PostTask(std::move(task));
+}
+
+}  // namespace impeller

impeller/base/work_queue_common.h

@@ -0,0 +1,33 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#pragma once
+
+#include <memory>
+
+#include "flutter/fml/concurrent_message_loop.h"
+#include "flutter/fml/macros.h"
+#include "impeller/base/work_queue.h"
+
+namespace impeller {
+
+class WorkQueueCommon : public WorkQueue {
+ public:
+  static std::shared_ptr<WorkQueueCommon> Create();
+
+  // |WorkQueue|
+  ~WorkQueueCommon();
+
+ private:
+  std::shared_ptr<fml::ConcurrentMessageLoop> loop_;
+
+  WorkQueueCommon();
+
+  // |WorkQueue|
+  void PostTask(fml::closure task) override;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(WorkQueueCommon);
+};
+
+}  // namespace impeller

impeller/renderer/backend/gles/context_gles.cc

@@ -6,6 +6,7 @@
 
 #include "impeller/base/config.h"
 #include "impeller/base/validation.h"
+#include "impeller/base/work_queue_common.h"
 
 namespace impeller {
 
@@ -52,12 +53,21 @@ ContextGLES::ContextGLES(
     }
   }
 
-  // Create the sampler library
+  // Create the sampler library.
   {
     sampler_library_ =
         std::shared_ptr<SamplerLibraryGLES>(new SamplerLibraryGLES());
   }
 
+  // Create the work queue.
+  {
+    work_queue_ = WorkQueueCommon::Create();
+    if (!work_queue_) {
+      VALIDATION_LOG << "Could not create work queue.";
+      return;
+    }
+  }
+
   is_valid_ = true;
 }
 
@@ -86,27 +96,37 @@ bool ContextGLES::IsValid() const {
   return is_valid_;
 }
 
+// |Context|
 std::shared_ptr<Allocator> ContextGLES::GetResourceAllocator() const {
   return resource_allocator_;
 }
 
+// |Context|
 std::shared_ptr<ShaderLibrary> ContextGLES::GetShaderLibrary() const {
   return shader_library_;
 }
 
+// |Context|
 std::shared_ptr<SamplerLibrary> ContextGLES::GetSamplerLibrary() const {
   return sampler_library_;
 }
 
+// |Context|
 std::shared_ptr<PipelineLibrary> ContextGLES::GetPipelineLibrary() const {
   return pipeline_library_;
 }
 
+// |Context|
 std::shared_ptr<CommandBuffer> ContextGLES::CreateCommandBuffer() const {
   return std::shared_ptr<CommandBufferGLES>(
       new CommandBufferGLES(weak_from_this(), reactor_));
 }
 
+// |Context|
+std::shared_ptr<WorkQueue> ContextGLES::GetWorkQueue() const {
+  return work_queue_;
+}
+
 // |Context|
 bool ContextGLES::HasThreadingRestrictions() const {
   return true;

impeller/renderer/backend/gles/context_gles.h

@@ -38,6 +38,7 @@ class ContextGLES final : public Context,
   std::shared_ptr<ShaderLibraryGLES> shader_library_;
   std::shared_ptr<PipelineLibraryGLES> pipeline_library_;
   std::shared_ptr<SamplerLibraryGLES> sampler_library_;
+  std::shared_ptr<WorkQueue> work_queue_;
   std::shared_ptr<AllocatorGLES> resource_allocator_;
   bool is_valid_ = false;
 
@@ -62,6 +63,9 @@ class ContextGLES final : public Context,
   // |Context|
   std::shared_ptr<CommandBuffer> CreateCommandBuffer() const override;
 
+  // |Context|
+  std::shared_ptr<WorkQueue> GetWorkQueue() const override;
+
   // |Context|
   bool HasThreadingRestrictions() const override;
 

impeller/renderer/backend/metal/context_mtl.h

@@ -42,6 +42,7 @@ class ContextMTL final : public Context,
   std::shared_ptr<PipelineLibraryMTL> pipeline_library_;
   std::shared_ptr<SamplerLibrary> sampler_library_;
   std::shared_ptr<AllocatorMTL> resource_allocator_;
+  std::shared_ptr<WorkQueue> work_queue_;
   bool is_valid_ = false;
 
   ContextMTL(id<MTLDevice> device, NSArray<id<MTLLibrary>>* shader_libraries);
@@ -64,6 +65,9 @@ class ContextMTL final : public Context,
   // |Context|
   std::shared_ptr<CommandBuffer> CreateCommandBuffer() const override;
 
+  // |Context|
+  std::shared_ptr<WorkQueue> GetWorkQueue() const override;
+
   std::shared_ptr<CommandBuffer> CreateCommandBufferInQueue(
       id<MTLCommandQueue> queue) const;