Use ThreadScheduler::Current() in bindings/.

This CL replaces the occurrences of "Platform::Current()
->CurrentThread()->Scheduler()" with "ThreadScheduler::Current()"
which has the same meaning.

Also, this CL simplifies the code that assumes Thread::Scheduler()
can be null, which is no longer true.

Bug: 826203
Change-Id: I994db5b3be6e5e0f29cfe346dac15b49ca40394e
Reviewed-on: https://chromium-review.googlesource.com/c/1314079Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Yuta Kitamura <yutak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605271}

third_party/blink/renderer/bindings/core/v8/v8_gc_for_context_dispose.cc

@@ -59,10 +59,9 @@ static size_t GetMemoryUsage() {
 namespace blink {
 
 V8GCForContextDispose::V8GCForContextDispose()
-    : pseudo_idle_timer_(
-          Platform::Current()->MainThread()->Scheduler()->V8TaskRunner(),
-          this,
-          &V8GCForContextDispose::PseudoIdleTimerFired),
+    : pseudo_idle_timer_(ThreadScheduler::Current()->V8TaskRunner(),
+                         this,
+                         &V8GCForContextDispose::PseudoIdleTimerFired),
       force_page_navigation_gc_(false) {
   Reset();
 }

third_party/blink/renderer/bindings/core/v8/v8_initializer.cc

@@ -695,9 +695,7 @@ void V8Initializer::InitializeMainThread(const intptr_t* reference_table) {
                                  v8_extras_mode, &array_buffer_allocator,
                                  reference_table);
 
-  // NOTE: Some threads (namely utility threads) don't have a scheduler.
-  ThreadScheduler* scheduler =
-      Platform::Current()->CurrentThread()->Scheduler();
+  ThreadScheduler* scheduler = ThreadScheduler::Current();
 
 #if defined(USE_V8_CONTEXT_SNAPSHOT)
   V8PerIsolateData::V8ContextSnapshotMode v8_context_snapshot_mode =
@@ -715,10 +713,8 @@ void V8Initializer::InitializeMainThread(const intptr_t* reference_table) {
       V8PerIsolateData::V8ContextSnapshotMode::kDontUseSnapshot;
 #endif  // USE_V8_CONTEXT_SNAPSHOT
 
-  v8::Isolate* isolate = V8PerIsolateData::Initialize(
-      scheduler ? scheduler->V8TaskRunner()
-                : Platform::Current()->CurrentThread()->GetTaskRunner(),
-      v8_context_snapshot_mode);
+  v8::Isolate* isolate = V8PerIsolateData::Initialize(scheduler->V8TaskRunner(),
+                                                      v8_context_snapshot_mode);
 
   // ThreadState::isolate_ needs to be set before setting the EmbedderHeapTracer
   // as setting the tracer indicates that a V8 garbage collection should trace