[scheduler] Rename blink::background_scheduler to worker_pool

The term "background" is confusing as it refers to a thread with a
specific priority. Use worker_pool instead to refer to
non-main-thread scheduler.

R=haraken@chromium.org,gab@chromium.org

Change-Id: Ia72090e39a3354cd14c539e64475cf661db15cd7
Reviewed-on: https://chromium-review.googlesource.com/c/1282396
Commit-Queue: Alexander Timin <altimin@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630516}

third_party/blink/renderer/bindings/core/v8/script_streamer.cc

@@ -21,9 +21,9 @@
 #include "third_party/blink/renderer/platform/loader/fetch/cached_metadata.h"
 #include "third_party/blink/renderer/platform/loader/fetch/resource.h"
 #include "third_party/blink/renderer/platform/runtime_enabled_features.h"
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
 #include "third_party/blink/renderer/platform/scheduler/public/thread_scheduler.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 #include "third_party/blink/renderer/platform/shared_buffer.h"
 #include "third_party/blink/renderer/platform/wtf/deque.h"
 #include "third_party/blink/renderer/platform/wtf/text/text_encoding_registry.h"
@@ -445,7 +445,7 @@ void ScriptStreamer::NotifyAppendData() {
       // cancel the task.
       //
       // TODO(leszeks): Decrease the priority of these tasks where possible.
-      background_scheduler::PostOnBackgroundThreadWithTraits(
+      worker_pool::PostTaskWithTraits(
           FROM_HERE, {base::TaskPriority::USER_BLOCKING, base::MayBlock()},
           CrossThreadBind(RunBlockingScriptStreamingTask,
                           WTF::Passed(std::move(script_streaming_task)),
@@ -498,7 +498,7 @@ void ScriptStreamer::NotifyFinished() {
       // The task creation shouldn't fail, since it didn't fail before during
       // NotifyAppendData.
       CHECK(script_streaming_task);
-      background_scheduler::PostOnBackgroundThreadWithTraits(
+      worker_pool::PostTaskWithTraits(
           FROM_HERE, {base::TaskPriority::USER_BLOCKING},
           CrossThreadBind(RunNonBlockingScriptStreamingTask,
                           WTF::Passed(std::move(script_streaming_task)),

third_party/blink/renderer/core/html/canvas/canvas_async_blob_creator.cc

@@ -20,10 +20,10 @@
 #include "third_party/blink/renderer/platform/graphics/skia/skia_utils.h"
 #include "third_party/blink/renderer/platform/histogram.h"
 #include "third_party/blink/renderer/platform/image-encoders/image_encoder_utils.h"
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
 #include "third_party/blink/renderer/platform/scheduler/public/thread.h"
 #include "third_party/blink/renderer/platform/scheduler/public/thread_scheduler.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 #include "third_party/blink/renderer/platform/wtf/functional.h"
 #include "third_party/blink/renderer/platform/wtf/time.h"
 #include "third_party/skia/include/core/SkSurface.h"
@@ -330,7 +330,7 @@ void CanvasAsyncBlobCreator::ScheduleAsyncBlobCreation(const double& quality) {
                         WrapPersistent(this)));
 
     } else {
-      background_scheduler::PostOnBackgroundThread(
+      worker_pool::PostTask(
           FROM_HERE,
           CrossThreadBind(&CanvasAsyncBlobCreator::EncodeImageOnEncoderThread,
                           WrapCrossThreadPersistent(this), quality));

third_party/blink/renderer/core/imagebitmap/image_bitmap.cc

@@ -17,8 +17,8 @@
 #include "third_party/blink/renderer/platform/graphics/canvas_resource_provider.h"
 #include "third_party/blink/renderer/platform/graphics/skia/skia_utils.h"
 #include "third_party/blink/renderer/platform/image-decoders/image_decoder.h"
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 #include "third_party/blink/renderer/platform/wtf/saturated_arithmetic.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkImageInfo.h"
@@ -1004,7 +1004,7 @@ ScriptPromise ImageBitmap::CreateAsync(ImageElementBase* image,
                                      draw_dst_rect, parsed_options.flip_y);
   std::unique_ptr<ParsedOptions> passed_parsed_options =
       std::make_unique<ParsedOptions>(parsed_options);
-  background_scheduler::PostOnBackgroundThread(
+  worker_pool::PostTask(
       FROM_HERE,
       CrossThreadBind(&RasterizeImageOnBackgroundThread,
                       WrapCrossThreadPersistent(resolver),

third_party/blink/renderer/core/imagebitmap/image_bitmap_factories.cc

@@ -52,9 +52,9 @@
 #include "third_party/blink/renderer/platform/cross_thread_functional.h"
 #include "third_party/blink/renderer/platform/histogram.h"
 #include "third_party/blink/renderer/platform/image-decoders/image_decoder.h"
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
 #include "third_party/blink/renderer/platform/scheduler/public/thread.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 #include "third_party/blink/renderer/platform/shared_buffer.h"
 #include "v8/include/v8.h"
 
@@ -314,7 +314,7 @@ void ImageBitmapFactories::ImageBitmapLoader::ScheduleAsyncImageBitmapDecoding(
     DOMArrayBuffer* array_buffer) {
   scoped_refptr<base::SingleThreadTaskRunner> task_runner =
       Thread::Current()->GetTaskRunner();
-  background_scheduler::PostOnBackgroundThread(
+  worker_pool::PostTask(
       FROM_HERE,
       CrossThreadBind(
           &ImageBitmapFactories::ImageBitmapLoader::DecodeImageOnDecoderThread,

third_party/blink/renderer/modules/background_fetch/background_fetch_icon_loader.cc

@@ -21,8 +21,8 @@
 #include "third_party/blink/renderer/platform/image-decoders/segment_reader.h"
 #include "third_party/blink/renderer/platform/loader/fetch/resource_loader_options.h"
 #include "third_party/blink/renderer/platform/loader/fetch/resource_request.h"
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 #include "third_party/blink/renderer/platform/weborigin/kurl.h"
 #include "third_party/blink/renderer/platform/wtf/text/string_impl.h"
 #include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"
@@ -164,7 +164,7 @@ void BackgroundFetchIconLoader::DidFinishLoading(
   scoped_refptr<base::SingleThreadTaskRunner> task_runner =
       Thread::Current()->GetTaskRunner();
 
-  background_scheduler::PostOnBackgroundThread(
+  worker_pool::PostTask(
       FROM_HERE,
       CrossThreadBind(
           &BackgroundFetchIconLoader::DecodeAndResizeImageOnBackgroundThread,

third_party/blink/renderer/modules/clipboard/clipboard_promise.cc

@@ -21,9 +21,9 @@
 #include "third_party/blink/renderer/platform/cross_thread_functional.h"
 #include "third_party/blink/renderer/platform/image-decoders/image_decoder.h"
 #include "third_party/blink/renderer/platform/image-encoders/image_encoder.h"
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
 #include "third_party/blink/renderer/platform/scheduler/public/thread.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 #include "third_party/blink/renderer/platform/wtf/functional.h"
 
 // And now, a brief note about clipboard permissions.
@@ -259,13 +259,13 @@ void ClipboardPromise::OnLoadBufferComplete(DOMArrayBuffer* array_buffer) {
   file_reader_.reset();
 
   if (blob_type == kMimeTypeImagePng) {
-    background_scheduler::PostOnBackgroundThread(
+    worker_pool::PostTask(
         FROM_HERE,
         CrossThreadBind(&ClipboardPromise::DecodeImageOnBackgroundThread,
                         WrapCrossThreadPersistent(this), GetTaskRunner(),
                         WrapCrossThreadPersistent(array_buffer)));
   } else if (blob_type == kMimeTypeTextPlain) {
-    background_scheduler::PostOnBackgroundThread(
+    worker_pool::PostTask(
         FROM_HERE,
         CrossThreadBind(&ClipboardPromise::DecodeTextOnBackgroundThread,
                         WrapCrossThreadPersistent(this), GetTaskRunner(),

third_party/blink/renderer/modules/webaudio/async_audio_decoder.cc

@@ -33,9 +33,9 @@
 #include "third_party/blink/renderer/platform/audio/audio_bus.h"
 #include "third_party/blink/renderer/platform/audio/audio_file_reader.h"
 #include "third_party/blink/renderer/platform/cross_thread_functional.h"
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
 #include "third_party/blink/renderer/platform/scheduler/public/thread.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 
 namespace blink {
 
@@ -55,7 +55,7 @@ void AsyncAudioDecoder::DecodeAsync(
       context->GetExecutionContext()->GetTaskRunner(
           blink::TaskType::kInternalMedia);
 
-  background_scheduler::PostOnBackgroundThread(
+  worker_pool::PostTask(
       FROM_HERE,
       CrossThreadBind(&AsyncAudioDecoder::DecodeOnBackgroundThread,
                       WrapCrossThreadPersistent(audio_data), sample_rate,

third_party/blink/renderer/platform/bindings/parkable_string.cc

@@ -16,9 +16,9 @@
 #include "third_party/blink/renderer/platform/bindings/parkable_string_manager.h"
 #include "third_party/blink/renderer/platform/cross_thread_functional.h"
 #include "third_party/blink/renderer/platform/instrumentation/tracing/web_process_memory_dump.h"
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
 #include "third_party/blink/renderer/platform/scheduler/public/thread.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 #include "third_party/blink/renderer/platform/wtf/address_sanitizer.h"
 #include "third_party/blink/renderer/platform/wtf/allocator/partitions.h"
 #include "third_party/blink/renderer/platform/wtf/thread_specific.h"
@@ -345,7 +345,7 @@ void ParkableStringImpl::ParkInternal(ParkingMode mode) {
     auto params = std::make_unique<CompressionTaskParams>(
         this, string_.Bytes(), string_.CharactersSizeInBytes(),
         Thread::Current()->GetTaskRunner());
-    background_scheduler::PostOnBackgroundThread(
+    worker_pool::PostTask(
         FROM_HERE, CrossThreadBind(&ParkableStringImpl::CompressInBackground,
                                    WTF::Passed(std::move(params))));
     state_ = State::kParkingInProgress;

third_party/blink/renderer/platform/scheduler/BUILD.gn

@@ -9,7 +9,6 @@ import("//third_party/protobuf/proto_library.gni")
 
 blink_platform_sources("scheduler") {
   sources = [
-    "common/background_scheduler.cc",
     "common/cancelable_closure_holder.cc",
     "common/cancelable_closure_holder.h",
     "common/features.cc",
@@ -56,6 +55,7 @@ blink_platform_sources("scheduler") {
     "common/unprioritized_resource_loading_task_runner_handle.h",
     "common/web_resource_loading_task_runner_handle.cc",
     "common/web_thread_scheduler.cc",
+    "common/worker_pool.cc",
     "main_thread/auto_advancing_virtual_time_domain.cc",
     "main_thread/auto_advancing_virtual_time_domain.h",
     "main_thread/deadline_task_runner.cc",
@@ -101,7 +101,6 @@ blink_platform_sources("scheduler") {
     "main_thread/web_render_widget_scheduling_state.cc",
     "main_thread/web_scoped_virtual_time_pauser.cc",
     "public/aggregated_metric_reporter.h",
-    "public/background_scheduler.h",
     "public/frame_or_worker_scheduler.h",
     "public/frame_scheduler.h",
     "public/frame_status.h",
@@ -114,6 +113,7 @@ blink_platform_sources("scheduler") {
     "public/thread.h",
     "public/thread_cpu_throttler.h",
     "public/thread_scheduler.h",
+    "public/worker_pool.h",
     "public/worker_scheduler.h",
     "worker/compositor_metrics_helper.cc",
     "worker/compositor_metrics_helper.h",
@@ -178,7 +178,6 @@ jumbo_source_set("unit_tests") {
   testonly = true
 
   sources = [
-    "common/background_scheduler_unittest.cc",
     "common/idle_helper_unittest.cc",
     "common/idle_memory_reclaimer_unittest.cc",
     "common/metrics_helper_unittest.cc",
@@ -188,6 +187,7 @@ jumbo_source_set("unit_tests") {
     "common/throttling/budget_pool_unittest.cc",
     "common/throttling/task_queue_throttler_unittest.cc",
     "common/tracing_helper_unittest.cc",
+    "common/worker_pool_unittest.cc",
     "main_thread/auto_advancing_virtual_time_domain_unittest.cc",
     "main_thread/deadline_task_runner_unittest.cc",
     "main_thread/frame_scheduler_impl_unittest.cc",

third_party/blink/renderer/platform/scheduler/TaskSchedulingInBlink.md

@@ -151,13 +151,15 @@ as we are focused on making freezing better instead.
 ## Off-main thread scheduling
 
 If your task doesn’t have to run on the main thread, use
-BackgroundScheduler::PostOnBackgroundThread, which uses a thread pool
+worker_pool::PostTask, which uses a thread pool
 behind the scenes.
 
 Do not create your own dedicated thread if you need ordering for your tasks,
-use BackgroundScheduler::CreateBackgroundTaskRunnerWithTraits instead —
+use worker_pool::CreateTaskRunnerWithTraits instead —
 this creates a sequence (virtual thread which can run tasks in order on
 any of the threads in the thread pool).
+(Note: this doesn't exist yet because we haven't encountered a use case in Blink
+which needs it. If you need one, please task to scheduler-dev@ and we'll add it).
 
 See [threading and tasks](../../../../../docs/threading_and_tasks.md) for
 more details.

third_party/blink/renderer/platform/scheduler/common/background_scheduler.cc → third_party/blink/renderer/platform/scheduler/common/worker_pool.cc

@@ -2,29 +2,28 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 
 #include "base/location.h"
 #include "base/task/post_task.h"
 
 namespace blink {
 
-namespace background_scheduler {
+namespace worker_pool {
 
-void PostOnBackgroundThread(const base::Location& location,
-                            CrossThreadClosure closure) {
-  PostOnBackgroundThreadWithTraits(
-      location, {base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
-      std::move(closure));
+void PostTask(const base::Location& location, CrossThreadClosure closure) {
+  PostTaskWithTraits(location,
+                     {base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
+                     std::move(closure));
 }
 
-void PostOnBackgroundThreadWithTraits(const base::Location& location,
-                                      const base::TaskTraits& traits,
-                                      CrossThreadClosure closure) {
+void PostTaskWithTraits(const base::Location& location,
+                        const base::TaskTraits& traits,
+                        CrossThreadClosure closure) {
   base::PostTaskWithTraits(location, traits,
                            ConvertToBaseCallback(std::move(closure)));
 }
 
-}  // namespace background_scheduler
+}  // namespace worker_pool
 
 }  // namespace blink

third_party/blink/renderer/platform/scheduler/common/background_scheduler_unittest.cc → third_party/blink/renderer/platform/scheduler/common/worker_pool_unittest.cc

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "third_party/blink/renderer/platform/scheduler/public/background_scheduler.h"
+#include "third_party/blink/renderer/platform/scheduler/public/worker_pool.h"
 
 #include <memory>
 #include "base/location.h"
@@ -24,7 +24,7 @@ void PingPongTask(WaitableEvent* done_event) {
 TEST(BackgroundSchedulerTest, RunOnBackgroundThread) {
   base::test::ScopedTaskEnvironment scoped_task_environment;
   std::unique_ptr<WaitableEvent> done_event = std::make_unique<WaitableEvent>();
-  background_scheduler::PostOnBackgroundThread(
+  worker_pool::PostTask(
       FROM_HERE,
       CrossThreadBind(&PingPongTask, CrossThreadUnretained(done_event.get())));
   // Test passes by not hanging on the following wait().

third_party/blink/renderer/platform/scheduler/public/background_scheduler.h → third_party/blink/renderer/platform/scheduler/public/worker_pool.h

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_PUBLIC_BACKGROUND_SCHEDULER_H_
-#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_PUBLIC_BACKGROUND_SCHEDULER_H_
+#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_PUBLIC_WORKER_POOL_H_
+#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_PUBLIC_WORKER_POOL_H_
 
 #include "base/location.h"
 #include "base/sequenced_task_runner.h"
@@ -13,26 +13,29 @@
 
 namespace blink {
 
-namespace background_scheduler {
+namespace worker_pool {
 
-// These are a thin wrapper around base::TaskScheduler to accomodate
-// Blink's CrossThreadClosure, which only allows background tasks
-// (i.e. tasks which are run off the main thread).
+// These are a thin wrapper around base::TaskScheduler to ensure that all
+// callers use WTF::CrossThreadBind instead of base::Bind to ensure that
+// all non-thread-safe objects are copied properly.
 //
-// Non-background tasks should be posted using another scheduler, e.g.
-// FrameShceduler.
-PLATFORM_EXPORT void PostOnBackgroundThread(const base::Location&,
-                                            CrossThreadClosure);
+// All tasks that do not care about which thread they are running on
+// (e.g. compressing/uncompressing tasks) use this API.
+//
+// Tasks that have to run on a specific thread (e.g. main thread, compositor
+// thread, dedicated worker thread) should be posted via other means
+// (e.g. FrameScheduler for main thread tasks).
+PLATFORM_EXPORT void PostTask(const base::Location&, CrossThreadClosure);
 
-PLATFORM_EXPORT void PostOnBackgroundThreadWithTraits(const base::Location&,
-                                                      const base::TaskTraits&,
-                                                      CrossThreadClosure);
+PLATFORM_EXPORT void PostTaskWithTraits(const base::Location&,
+                                        const base::TaskTraits&,
+                                        CrossThreadClosure);
 
-// TODO(altimin): Expose CreateBackgroundTaskRunnerWithTraits when the
+// TODO(altimin): Expose CreateSequencedTaskRunnerWithTraits when the
 // need arises.
 
-}  // namespace background_scheduler
+}  // namespace worker_pool
 
 }  // namespace blink
 
-#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_PUBLIC_BACKGROUND_SCHEDULER_H_
+#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_PUBLIC_WORKER_POOL_H_

third_party/blink/tools/blinkpy/presubmit/audit_non_blink_usage.py

@@ -236,7 +236,6 @@ _CONFIG = [
             'url::.+',
 
             # Nested namespaces under the blink namespace
-            'background_scheduler::.+',
             'canvas_heuristic_parameters::.+',
             'compositor_target_property::.+',
             'cors::.+',
@@ -264,11 +263,12 @@ _CONFIG = [
             'style_change_extra_data::.+',
             'style_change_reason::.+',
             'svg_path_parser::.+',
-            'trace_event::.+',
             'touch_action_util::.+',
+            'trace_event::.+',
             'unicode::.+',
             'vector_math::.+',
             'web_core_test_support::.+',
+            'worker_pool::.+',
             'xpath::.+',
             '[a-z_]+_names::.+',