Rename BackgroundScheduler namepsace to background_scheduler

https://google.github.io/styleguide/cppguide.html#Namespace_Names
> Namespace names are all lower-case.

This CL has no behavior changes.

Bug: 889726
Change-Id: Idbe50cad950947ba8633758dbf7070d2288fa6d0
Reviewed-on: https://chromium-review.googlesource.com/c/1298946Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Zhuoyu Qian <zhuoyu.qian@samsung.com>
Cr-Commit-Position: refs/heads/master@{#602973}

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

@@ -424,7 +424,7 @@ void ScriptStreamer::NotifyAppendData(ScriptResource* resource) {
       // cancel the task.
       //
       // TODO(leszeks): Decrease the priority of these tasks where possible.
-      BackgroundScheduler::PostOnBackgroundThreadWithTraits(
+      background_scheduler::PostOnBackgroundThreadWithTraits(
           FROM_HERE, {base::TaskPriority::USER_BLOCKING, base::MayBlock()},
           CrossThreadBind(RunBlockingScriptStreamingTask,
                           WTF::Passed(std::move(script_streaming_task)),
@@ -476,7 +476,7 @@ void ScriptStreamer::NotifyFinished() {
       // The task creation shouldn't fail, since it didn't fail before during
       // NotifyAppendData.
       CHECK(script_streaming_task);
-      BackgroundScheduler::PostOnBackgroundThreadWithTraits(
+      background_scheduler::PostOnBackgroundThreadWithTraits(
           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

@@ -340,7 +340,7 @@ void CanvasAsyncBlobCreator::ScheduleAsyncBlobCreation(const double& quality) {
                         WrapPersistent(this)));
 
     } else {
-      BackgroundScheduler::PostOnBackgroundThread(
+      background_scheduler::PostOnBackgroundThread(
           FROM_HERE,
           CrossThreadBind(&CanvasAsyncBlobCreator::EncodeImageOnEncoderThread,
                           WrapCrossThreadPersistent(this), quality));

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

@@ -974,7 +974,7 @@ 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);
-  BackgroundScheduler::PostOnBackgroundThread(
+  background_scheduler::PostOnBackgroundThread(
       FROM_HERE,
       CrossThreadBind(&RasterizeImageOnBackgroundThread,
                       WrapCrossThreadPersistent(resolver),

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

@@ -296,7 +296,7 @@ void ImageBitmapFactories::ImageBitmapLoader::ScheduleAsyncImageBitmapDecoding(
     DOMArrayBuffer* array_buffer) {
   scoped_refptr<base::SingleThreadTaskRunner> task_runner =
       Platform::Current()->CurrentThread()->GetTaskRunner();
-  BackgroundScheduler::PostOnBackgroundThread(
+  background_scheduler::PostOnBackgroundThread(
       FROM_HERE,
       CrossThreadBind(
           &ImageBitmapFactories::ImageBitmapLoader::DecodeImageOnDecoderThread,

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

@@ -162,7 +162,7 @@ void BackgroundFetchIconLoader::DidFinishLoading(
   scoped_refptr<base::SingleThreadTaskRunner> task_runner =
       Platform::Current()->CurrentThread()->GetTaskRunner();
 
-  BackgroundScheduler::PostOnBackgroundThread(
+  background_scheduler::PostOnBackgroundThread(
       FROM_HERE,
       CrossThreadBind(
           &BackgroundFetchIconLoader::DecodeAndResizeImageOnBackgroundThread,

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

@@ -55,7 +55,7 @@ void AsyncAudioDecoder::DecodeAsync(
       context->GetExecutionContext()->GetTaskRunner(
           blink::TaskType::kInternalMedia);
 
-  BackgroundScheduler::PostOnBackgroundThread(
+  background_scheduler::PostOnBackgroundThread(
       FROM_HERE,
       CrossThreadBind(&AsyncAudioDecoder::DecodeOnBackgroundThread,
                       WrapCrossThreadPersistent(audio_data), sample_rate,

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

@@ -9,14 +9,15 @@
 
 namespace blink {
 
-void BackgroundScheduler::PostOnBackgroundThread(const base::Location& location,
-                                                 CrossThreadClosure closure) {
+void background_scheduler::PostOnBackgroundThread(
+    const base::Location& location,
+    CrossThreadClosure closure) {
   PostOnBackgroundThreadWithTraits(
       location, {base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
       std::move(closure));
 }
 
-void BackgroundScheduler::PostOnBackgroundThreadWithTraits(
+void background_scheduler::PostOnBackgroundThreadWithTraits(
     const base::Location& location,
     const base::TaskTraits& traits,
     CrossThreadClosure closure) {

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

@@ -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>();
-  BackgroundScheduler::PostOnBackgroundThread(
+  background_scheduler::PostOnBackgroundThread(
       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

@@ -13,7 +13,7 @@
 
 namespace blink {
 
-namespace BackgroundScheduler {
+namespace background_scheduler {
 
 // These are a thin wrapper around base::TaskScheduler to accomodate
 // Blink's CrossThreadClosure, which only allows background tasks
@@ -31,7 +31,7 @@ PLATFORM_EXPORT void PostOnBackgroundThreadWithTraits(const base::Location&,
 // TODO(altimin): Expose CreateBackgroundTaskRunnerWithTraits when the
 // need arises.
 
-}  // namespace BackgroundScheduler
+}  // namespace background_scheduler
 
 }  // namespace blink
 

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

@@ -220,6 +220,7 @@ _CONFIG = [
             'url::.+',
 
             # Nested namespaces under the blink namespace
+            'background_scheduler::.+',
             'canvas_heuristic_parameters::.+',
             'cssvalue::.+',
             'encoding::.+',