Add and plumb empty DawnContextProvider

Prepare for Dawn as an option for compositing and raster by creating an
empty implementation of the DawnContextProvider, which will use the Skia
Dawn backend to create a GrContext.

Compilation of DawnContextProvider and the Skia Dawn backend are enabled
with the gn arg use_skia_dawn=true. The command line flag
--gr-context-type=dawn will select SkiaRenderer Dawn at runtime.

For now it doesn't connect with Dawn, and DawnContextProvider::Create()
always returns nullptr.

See crrev.com/c/1873874 for context.

Bug: 1021566
Change-Id: Ifa8e17e5e8b8b3461f4177956a8e28f5bd8d27c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1896120
Commit-Queue: Sean Gilhuly <sgilhuly@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Reviewed-by: Jonathan Backer <backer@chromium.org>
Reviewed-by: Stephen White <senorblanco@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713020}

components/viz/common/BUILD.gn

@@ -4,6 +4,7 @@
 
 import("//components/viz/viz.gni")
 import("//gpu/vulkan/features.gni")
+import("//skia/features.gni")
 import("//testing/test.gni")
 
 source_set("resource_format") {
@@ -40,6 +41,8 @@ viz_component("resource_format_utils") {
   ]
 }
 
+# TODO(sgilhuly): To reduce link times, merge these context provider components
+# into a single gr_context_provider component.
 if (is_mac) {
   viz_component("metal_context_provider") {
     output_name = "viz_metal_context_provider"
@@ -107,6 +110,28 @@ if (enable_vulkan) {
   }
 }
 
+if (skia_use_dawn) {
+  viz_component("dawn_context_provider") {
+    output_name = "viz_dawn_context_provider"
+
+    defines = [ "VIZ_DAWN_CONTEXT_PROVIDER_IMPLEMENTATION" ]
+
+    sources = [
+      "gpu/dawn_context_provider.cc",
+      "gpu/dawn_context_provider.h",
+      "viz_dawn_context_provider_export.h",
+    ]
+
+    public_deps = [
+      "//skia",
+    ]
+
+    deps = [
+      "//base",
+    ]
+  }
+}
+
 viz_component("common") {
   output_name = "viz_common"
 
@@ -302,6 +327,9 @@ viz_component("common") {
   if (is_mac) {
     public_deps += [ ":metal_context_provider" ]
   }
+  if (skia_use_dawn) {
+    public_deps += [ ":dawn_context_provider" ]
+  }
 }
 
 viz_source_set("unit_tests") {

components/viz/common/gpu/dawn_context_provider.cc

+// Copyright (c) 2019 The Chromium 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 "components/viz/common/gpu/dawn_context_provider.h"
+
+#include "base/memory/ptr_util.h"
+
+namespace viz {
+
+std::unique_ptr<DawnContextProvider> DawnContextProvider::Create() {
+  auto context_provider = base::WrapUnique(new DawnContextProvider());
+  if (!context_provider->IsValid())
+    return nullptr;
+  return context_provider;
+}
+
+DawnContextProvider::DawnContextProvider() = default;
+
+DawnContextProvider::~DawnContextProvider() = default;
+
+}  // namespace viz

components/viz/common/gpu/dawn_context_provider.h

+// Copyright (c) 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_VIZ_COMMON_GPU_DAWN_CONTEXT_PROVIDER_H_
+#define COMPONENTS_VIZ_COMMON_GPU_DAWN_CONTEXT_PROVIDER_H_
+
+#include "base/macros.h"
+#include "components/viz/common/viz_dawn_context_provider_export.h"
+#include "third_party/skia/include/gpu/GrContext.h"
+
+class GrContext;
+
+namespace viz {
+
+class VIZ_DAWN_CONTEXT_PROVIDER_EXPORT DawnContextProvider {
+ public:
+  static std::unique_ptr<DawnContextProvider> Create();
+  ~DawnContextProvider();
+
+  GrContext* GetGrContext() { return gr_context_.get(); }
+  bool IsValid() { return !!gr_context_; }
+
+ private:
+  DawnContextProvider();
+
+  sk_sp<GrContext> gr_context_;
+
+  DISALLOW_COPY_AND_ASSIGN(DawnContextProvider);
+};
+
+}  // namespace viz
+
+#endif  // COMPONENTS_VIZ_COMMON_GPU_DAWN_CONTEXT_PROVIDER_H_

components/viz/common/viz_dawn_context_provider_export.h

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_VIZ_COMMON_VIZ_DAWN_CONTEXT_PROVIDER_EXPORT_H_
+#define COMPONENTS_VIZ_COMMON_VIZ_DAWN_CONTEXT_PROVIDER_EXPORT_H_
+
+#if defined(COMPONENT_BUILD)
+#if defined(WIN32)
+
+#if defined(VIZ_DAWN_CONTEXT_PROVIDER_IMPLEMENTATION)
+#define VIZ_DAWN_CONTEXT_PROVIDER_EXPORT __declspec(dllexport)
+#else
+#define VIZ_DAWN_CONTEXT_PROVIDER_EXPORT __declspec(dllimport)
+#endif  // defined(VIZ_DAWN_CONTEXT_PROVIDER_IMPLEMENTATION)
+
+#else  // defined(WIN32)
+#if defined(VIZ_DAWN_CONTEXT_PROVIDER_IMPLEMENTATION)
+#define VIZ_DAWN_CONTEXT_PROVIDER_EXPORT __attribute__((visibility("default")))
+#else
+#define VIZ_DAWN_CONTEXT_PROVIDER_EXPORT
+#endif
+#endif
+
+#else  // defined(COMPONENT_BUILD)
+#define VIZ_DAWN_CONTEXT_PROVIDER_EXPORT
+#endif
+
+#endif  // COMPONENTS_VIZ_COMMON_VIZ_DAWN_CONTEXT_PROVIDER_EXPORT_H_

gpu/command_buffer/service/BUILD.gn

@@ -5,6 +5,7 @@
 import("//build/config/jumbo.gni")
 import("//build/config/ui.gni")
 import("//gpu/vulkan/features.gni")
+import("//skia/features.gni")
 import("//third_party/protobuf/proto_library.gni")
 import("//ui/gl/features.gni")
 
@@ -309,6 +310,7 @@ target(link_target_type, "gles2_sources") {
     "//gpu/config",
     "//gpu/ipc/common",
     "//gpu/vulkan:buildflags",
+    "//skia:buildflags",
     "//third_party/angle:angle_image_util",
     "//third_party/angle:commit_id",
     "//third_party/angle:translator",
@@ -371,6 +373,10 @@ target(link_target_type, "gles2_sources") {
     ]
   }
 
+  if (skia_use_dawn) {
+    deps += [ "//components/viz/common:dawn_context_provider" ]
+  }
+
   if (is_android) {
     if (!is_debug) {
       # On Android optimize more since this component can be a bottleneck.

gpu/command_buffer/service/DEPS

 include_rules = [
   "+cc/paint",
+  "+skia",
   "+third_party/skia",
   "+components/crash/core/common/crash_key.h",
+  "+components/viz/common/gpu/dawn_context_provider.h",
   "+components/viz/common/gpu/metal_context_provider.h",
   "+components/viz/common/gpu/vulkan_context_provider.h",
   "+components/viz/common/resources/resource_format.h",

gpu/command_buffer/service/gpu_switches.cc

@@ -67,6 +67,7 @@ const char kGrContextType[] = "gr-context-type";
 const char kGrContextTypeGL[] = "gl";
 const char kGrContextTypeVulkan[] = "vulkan";
 const char kGrContextTypeMetal[] = "metal";
+const char kGrContextTypeDawn[] = "dawn";
 // Enable Vulkan support and select Vulkan implementation, must also have
 // ENABLE_VULKAN defined.
 const char kUseVulkan[] = "use-vulkan";

gpu/command_buffer/service/gpu_switches.h

@@ -32,6 +32,7 @@ GPU_EXPORT extern const char kGrContextType[];
 GPU_EXPORT extern const char kGrContextTypeGL[];
 GPU_EXPORT extern const char kGrContextTypeVulkan[];
 GPU_EXPORT extern const char kGrContextTypeMetal[];
+GPU_EXPORT extern const char kGrContextTypeDawn[];
 GPU_EXPORT extern const char kVulkanImplementationNameNative[];
 GPU_EXPORT extern const char kUseVulkan[];
 GPU_EXPORT extern const char kVulkanImplementationNameNative[];

gpu/command_buffer/service/service_utils.cc

@@ -179,6 +179,8 @@ GpuPreferences ParseGpuPreferences(const base::CommandLine* command_line) {
           << "GrContextType is Metal, but Metal is not enabled.";
       gpu_preferences.gr_context_type = GrContextType::kMetal;
 #endif
+    } else if (value == switches::kGrContextTypeDawn) {
+      gpu_preferences.gr_context_type = GrContextType::kDawn;
     } else {
       NOTREACHED() << "Invalid GrContextType.";
       gpu_preferences.gr_context_type = GrContextType::kGL;

gpu/command_buffer/service/shared_context_state.cc

@@ -13,6 +13,7 @@
 #include "gpu/command_buffer/service/service_utils.h"
 #include "gpu/config/gpu_driver_bug_workarounds.h"
 #include "gpu/vulkan/buildflags.h"
+#include "skia/buildflags.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/gl_share_group.h"
@@ -28,6 +29,10 @@
 #include "components/viz/common/gpu/metal_context_provider.h"
 #endif
 
+#if BUILDFLAG(SKIA_USE_DAWN)
+#include "components/viz/common/gpu/dawn_context_provider.h"
+#endif
+
 namespace {
 static constexpr size_t kInitialScratchDeserializationBufferSize = 1024;
 }
@@ -51,12 +56,14 @@ SharedContextState::SharedContextState(
     base::OnceClosure context_lost_callback,
     GrContextType gr_context_type,
     viz::VulkanContextProvider* vulkan_context_provider,
-    viz::MetalContextProvider* metal_context_provider)
+    viz::MetalContextProvider* metal_context_provider,
+    viz::DawnContextProvider* dawn_context_provider)
     : use_virtualized_gl_contexts_(use_virtualized_gl_contexts),
       context_lost_callback_(std::move(context_lost_callback)),
       gr_context_type_(gr_context_type),
       vk_context_provider_(vulkan_context_provider),
       metal_context_provider_(metal_context_provider),
+      dawn_context_provider_(dawn_context_provider),
       share_group_(std::move(share_group)),
       context_(context),
       real_context_(std::move(context)),
@@ -77,6 +84,13 @@ SharedContextState::SharedContextState(
     use_virtualized_gl_contexts_ = false;
     DCHECK(gr_context_);
   }
+  if (GrContextIsDawn()) {
+#if BUILDFLAG(SKIA_USE_DAWN)
+    gr_context_ = dawn_context_provider_->GetGrContext();
+#endif
+    use_virtualized_gl_contexts_ = false;
+    DCHECK(gr_context_);
+  }
 
   if (base::ThreadTaskRunnerHandle::IsSet()) {
     base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(

gpu/command_buffer/service/shared_context_state.h

@@ -28,6 +28,7 @@ class GLSurface;
 }  // namespace gl
 
 namespace viz {
+class DawnContextProvider;
 class MetalContextProvider;
 class VulkanContextProvider;
 }  // namespace viz
@@ -58,7 +59,8 @@ class GPU_GLES2_EXPORT SharedContextState
       base::OnceClosure context_lost_callback,
       GrContextType gr_context_type = GrContextType::kGL,
       viz::VulkanContextProvider* vulkan_context_provider = nullptr,
-      viz::MetalContextProvider* metal_context_provider = nullptr);
+      viz::MetalContextProvider* metal_context_provider = nullptr,
+      viz::DawnContextProvider* dawn_context_provider = nullptr);
 
   void InitializeGrContext(const GpuDriverBugWorkarounds& workarounds,
                            GrContextOptions::PersistentCache* cache,
@@ -71,8 +73,10 @@ class GPU_GLES2_EXPORT SharedContextState
     return vk_context_provider_ && gr_context_type_ == GrContextType::kVulkan;
   }
   bool GrContextIsMetal() const {
-    return metal_context_provider_ &&
-        gr_context_type_ == GrContextType::kMetal;
+    return metal_context_provider_ && gr_context_type_ == GrContextType::kMetal;
+  }
+  bool GrContextIsDawn() const {
+    return dawn_context_provider_ && gr_context_type_ == GrContextType::kDawn;
   }
 
   bool InitializeGL(const GpuPreferences& gpu_preferences,
@@ -98,6 +102,9 @@ class GPU_GLES2_EXPORT SharedContextState
   viz::MetalContextProvider* metal_context_provider() {
     return metal_context_provider_;
   }
+  viz::DawnContextProvider* dawn_context_provider() {
+    return dawn_context_provider_;
+  }
   gl::ProgressReporter* progress_reporter() const { return progress_reporter_; }
   GrContext* gr_context() { return gr_context_; }
   // Handles Skia-reported shader compilation errors.
@@ -170,6 +177,7 @@ class GPU_GLES2_EXPORT SharedContextState
   GrContextType gr_context_type_ = GrContextType::kGL;
   viz::VulkanContextProvider* const vk_context_provider_;
   viz::MetalContextProvider* const metal_context_provider_;
+  viz::DawnContextProvider* const dawn_context_provider_;
   GrContext* gr_context_ = nullptr;
 
   scoped_refptr<gl::GLShareGroup> share_group_;

gpu/config/gpu_preferences.h

@@ -41,7 +41,8 @@ enum class GrContextType : uint32_t {
   kGL = 0,
   kVulkan = 1,
   kMetal = 2,
-  kLast = kMetal,
+  kDawn = 3,
+  kLast = kDawn,
 };
 
 // NOTE: if you modify this structure then you must also modify the

gpu/ipc/common/gpu_preferences.mojom

@@ -24,7 +24,8 @@ enum GrContextType {
   kGL = 0,
   kVulkan = 1,
   kMetal = 2,
-  kLast = kMetal,
+  kDawn = 3,
+  kLast = kDawn,
 };
 
 // gpu::GpuPreferences

gpu/ipc/common/gpu_preferences_mojom_traits.h

@@ -28,6 +28,8 @@ struct EnumTraits<gpu::mojom::GrContextType, gpu::GrContextType> {
         return gpu::mojom::GrContextType::kVulkan;
       case gpu::GrContextType::kMetal:
         return gpu::mojom::GrContextType::kMetal;
+      case gpu::GrContextType::kDawn:
+        return gpu::mojom::GrContextType::kDawn;
     }
     NOTREACHED();
     return gpu::mojom::GrContextType::kGL;
@@ -44,6 +46,9 @@ struct EnumTraits<gpu::mojom::GrContextType, gpu::GrContextType> {
       case gpu::mojom::GrContextType::kMetal:
         *out = gpu::GrContextType::kMetal;
         return true;
+      case gpu::mojom::GrContextType::kDawn:
+        *out = gpu::GrContextType::kDawn;
+        return true;
     }
     return false;
   }

gpu/ipc/service/gpu_channel_manager.cc

@@ -110,7 +110,8 @@ GpuChannelManager::GpuChannelManager(
     scoped_refptr<gl::GLSurface> default_offscreen_surface,
     ImageDecodeAcceleratorWorker* image_decode_accelerator_worker,
     viz::VulkanContextProvider* vulkan_context_provider,
-    viz::MetalContextProvider* metal_context_provider)
+    viz::MetalContextProvider* metal_context_provider,
+    viz::DawnContextProvider* dawn_context_provider)
     : task_runner_(task_runner),
       io_task_runner_(io_task_runner),
       gpu_preferences_(gpu_preferences),
@@ -133,7 +134,8 @@ GpuChannelManager::GpuChannelManager(
           base::BindRepeating(&GpuChannelManager::HandleMemoryPressure,
                               base::Unretained(this))),
       vulkan_context_provider_(vulkan_context_provider),
-      metal_context_provider_(metal_context_provider) {
+      metal_context_provider_(metal_context_provider),
+      dawn_context_provider_(dawn_context_provider) {
   DCHECK(task_runner->BelongsToCurrentThread());
   DCHECK(io_task_runner);
   DCHECK(scheduler);
@@ -481,8 +483,8 @@ scoped_refptr<SharedContextState> GpuChannelManager::GetSharedContextState(
       use_virtualized_gl_contexts,
       base::BindOnce(&GpuChannelManager::OnContextLost, base::Unretained(this),
                      /*synthetic_loss=*/false),
-      gpu_preferences_.gr_context_type,
-      vulkan_context_provider_, metal_context_provider_);
+      gpu_preferences_.gr_context_type, vulkan_context_provider_,
+      metal_context_provider_, dawn_context_provider_);
 
   // OOP-R needs GrContext for raster tiles.
   bool need_gr_context =

gpu/ipc/service/gpu_channel_manager.h

@@ -83,7 +83,8 @@ class GPU_IPC_SERVICE_EXPORT GpuChannelManager
       scoped_refptr<gl::GLSurface> default_offscreen_surface,
       ImageDecodeAcceleratorWorker* image_decode_accelerator_worker,
       viz::VulkanContextProvider* vulkan_context_provider = nullptr,
-      viz::MetalContextProvider* metal_context_provider = nullptr);
+      viz::MetalContextProvider* metal_context_provider = nullptr,
+      viz::DawnContextProvider* dawn_context_provider = nullptr);
   ~GpuChannelManager() override;
 
   GpuChannelManagerDelegate* delegate() const { return delegate_; }
@@ -296,6 +297,10 @@ class GPU_IPC_SERVICE_EXPORT GpuChannelManager
   // viz::GpuServiceImpl. The raster decoders will use it for rasterization.
   viz::MetalContextProvider* metal_context_provider_ = nullptr;
 
+  // With --gr-context-type=dawn, |dawn_context_provider_| will be set from
+  // viz::GpuServiceImpl. The raster decoders will use it for rasterization.
+  viz::DawnContextProvider* dawn_context_provider_ = nullptr;
+
   GpuPeakMemoryMonitor peak_memory_monitor_;
 
   // Member variables should appear before the WeakPtrFactory, to ensure

skia/BUILD.gn

@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/buildflag_header.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/features.gni")
 import("//build/config/freetype/freetype.gni")
@@ -11,6 +12,7 @@ import("//printing/buildflags/buildflags.gni")
 import("//testing/test.gni")
 import("//third_party/skia/gn/shared_sources.gni")
 import("//third_party/skia/third_party/skcms/skcms.gni")
+import("features.gni")
 
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
@@ -26,7 +28,12 @@ skia_support_skottie = true
 declare_args() {
   enable_skia_wuffs_gif = false
   skia_whitelist_serialized_typefaces = false
-  skia_use_dawn = false
+}
+
+# Generate a buildflag header for compile-time checking of Dawn support.
+buildflag_header("buildflags") {
+  header = "buildflags.h"
+  flags = [ "SKIA_USE_DAWN=$skia_use_dawn" ]
 }
 
 # External-facing config for dependent code.

skia/features.gni

+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+declare_args() {
+  # Enable experimental SkiaRenderer Dawn backend.
+  skia_use_dawn = false
+}