Revert of Add a WorkerScheduler and a WebThreadImplForWorker (patchset #16 id:380001 of https://codereview.chromium.org/1033643004/)

Reason for revert:
Looks like this broke ImageFrameGeneratorTest.incompleteDecodeBecomesCompleteMultiThreaded

Original issue's description:
> Add a WorkerScheduler and a WebThreadImplForWorker
>
> Adds a simple WorkerScheduler which supports Default and Idle Tasks (via
> Long Idle Periods). A follow up Blink patch will refactor
> WorkerThread.cpp to use these Idle Tasks.
>
> A WorkerSceduler is a pre-requisite for refactoring away the Blink
> Timer Heap as described in:
> https://docs.google.com/document/d/163ow-1wjd6L0rAN3V_U6t12eqVkq4mXDDjVaA4OuvCA/edit?usp=sharing
>
> BUG=463143
>
> Committed: https://crrev.com/510ed9c42029e1b2924ac05082c958591f029624
> Cr-Commit-Position: refs/heads/master@{#324847}
>
> Committed: https://crrev.com/b37d4c285dc2f505b006187d2651f6db96d9a42c
> Cr-Commit-Position: refs/heads/master@{#325026}

TBR=jochen@chromium.org,rmcilroy@chromium.org,skyostil@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=463143

Review URL: https://codereview.chromium.org/1088933002

Cr-Commit-Position: refs/heads/master@{#325037}

4 files changed, 27 insertions, 36 deletions

diff --git a/content/renderer/scheduler/renderer_scheduler_impl.h b/content/renderer/scheduler/renderer_scheduler_impl.h
index 9c3fc12..e4fd630 100644
--- a/content/renderer/scheduler/renderer_scheduler_impl.h
+++ b/content/renderer/scheduler/renderer_scheduler_impl.h
@@ -99,7 +99,6 @@ class CONTENT_EXPORT RendererSchedulerImpl
   bool CanEnterLongIdlePeriod(
       base::TimeTicks now,
       base::TimeDelta* next_long_idle_period_delay_out) override;
-  void IsNotQuiescent() override {}
 
   // Returns the serialized scheduler state for tracing.
   scoped_refptr<base::trace_event::ConvertableToTraceFormat> AsValueLocked(
diff --git a/content/renderer/scheduler/webthread_impl_for_renderer_scheduler.cc b/content/renderer/scheduler/webthread_impl_for_scheduler.cc
index 4855df19..b328142 100644
--- a/content/renderer/scheduler/webthread_impl_for_renderer_scheduler.cc
+++ b/content/renderer/scheduler/webthread_impl_for_scheduler.cc
@@ -2,49 +2,42 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "content/renderer/scheduler/webthread_impl_for_renderer_scheduler.h"
+#include "content/renderer/scheduler/webthread_impl_for_scheduler.h"
 
 #include "content/renderer/scheduler/renderer_scheduler.h"
 #include "third_party/WebKit/public/platform/WebTraceLocation.h"
 
 namespace content {
 
-WebThreadImplForRendererScheduler::WebThreadImplForRendererScheduler(
+WebThreadImplForScheduler::WebThreadImplForScheduler(
     RendererScheduler* scheduler)
     : task_runner_(scheduler->DefaultTaskRunner()),
-      idle_task_runner_(scheduler->IdleTaskRunner()),
       scheduler_(scheduler),
       thread_id_(base::PlatformThread::CurrentId()) {
 }
 
-WebThreadImplForRendererScheduler::~WebThreadImplForRendererScheduler() {
+WebThreadImplForScheduler::~WebThreadImplForScheduler() {
 }
 
-blink::PlatformThreadId WebThreadImplForRendererScheduler::threadId() const {
+blink::PlatformThreadId WebThreadImplForScheduler::threadId() const {
   return thread_id_;
 }
 
-base::MessageLoop* WebThreadImplForRendererScheduler::MessageLoop() const {
+base::MessageLoop* WebThreadImplForScheduler::MessageLoop() const {
   DCHECK(isCurrentThread());
   return base::MessageLoop::current();
 }
 
-base::SingleThreadTaskRunner* WebThreadImplForRendererScheduler::TaskRunner()
-    const {
+base::SingleThreadTaskRunner* WebThreadImplForScheduler::TaskRunner() const {
   return task_runner_.get();
 }
 
-SingleThreadIdleTaskRunner* WebThreadImplForRendererScheduler::IdleTaskRunner()
-    const {
-  return idle_task_runner_.get();
-}
-
-void WebThreadImplForRendererScheduler::AddTaskObserverInternal(
+void WebThreadImplForScheduler::AddTaskObserverInternal(
     base::MessageLoop::TaskObserver* observer) {
   scheduler_->AddTaskObserver(observer);
 }
 
-void WebThreadImplForRendererScheduler::RemoveTaskObserverInternal(
+void WebThreadImplForScheduler::RemoveTaskObserverInternal(
     base::MessageLoop::TaskObserver* observer) {
   scheduler_->RemoveTaskObserver(observer);
 }
diff --git a/content/renderer/scheduler/webthread_impl_for_renderer_scheduler.h b/content/renderer/scheduler/webthread_impl_for_scheduler.h
index 4b8d9fb..36bd2e2 100644
--- a/content/renderer/scheduler/webthread_impl_for_renderer_scheduler.h
+++ b/content/renderer/scheduler/webthread_impl_for_scheduler.h
@@ -2,27 +2,27 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CONTENT_RENDERER_SCHEDULER_WEBTHREAD_IMPL_FOR_RENDERER_SCHEDULER_H_
-#define CONTENT_RENDERER_SCHEDULER_WEBTHREAD_IMPL_FOR_RENDERER_SCHEDULER_H_
+#ifndef CONTENT_RENDERER_SCHEDULER_WEBTHREAD_IMPL_FOR_SCHEDULER_H_
+#define CONTENT_RENDERER_SCHEDULER_WEBTHREAD_IMPL_FOR_SCHEDULER_H_
+
+#include "content/child/webthread_impl.h"
 
 #include "base/containers/scoped_ptr_hash_map.h"
-#include "content/child/webthread_base.h"
 
 namespace content {
 
 class RendererScheduler;
 
-class CONTENT_EXPORT WebThreadImplForRendererScheduler : public WebThreadBase {
+class CONTENT_EXPORT WebThreadImplForScheduler : public WebThreadBase {
  public:
-  explicit WebThreadImplForRendererScheduler(RendererScheduler* scheduler);
-  virtual ~WebThreadImplForRendererScheduler();
+  explicit WebThreadImplForScheduler(RendererScheduler* scheduler);
+  virtual ~WebThreadImplForScheduler();
 
   // blink::WebThread implementation.
   blink::PlatformThreadId threadId() const override;
 
   // WebThreadBase implementation.
   base::SingleThreadTaskRunner* TaskRunner() const override;
-  SingleThreadIdleTaskRunner* IdleTaskRunner() const override;
 
  private:
   base::MessageLoop* MessageLoop() const override;
@@ -32,11 +32,10 @@ class CONTENT_EXPORT WebThreadImplForRendererScheduler : public WebThreadBase {
       base::MessageLoop::TaskObserver* observer) override;
 
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-  scoped_refptr<SingleThreadIdleTaskRunner> idle_task_runner_;
   RendererScheduler* scheduler_;  // Not owned.
   blink::PlatformThreadId thread_id_;
 };
 
 }  // namespace content
 
-#endif  // CONTENT_RENDERER_SCHEDULER_WEBTHREAD_IMPL_FOR_RENDERER_SCHEDULER_H_
+#endif  // CONTENT_RENDERER_SCHEDULER_WEBTHREAD_IMPL_FOR_SCHEDULER_H_
diff --git a/content/renderer/scheduler/webthread_impl_for_renderer_scheduler_unittest.cc b/content/renderer/scheduler/webthread_impl_for_scheduler_unittest.cc
index 191a271..e9e359a 100644
--- a/content/renderer/scheduler/webthread_impl_for_renderer_scheduler_unittest.cc
+++ b/content/renderer/scheduler/webthread_impl_for_scheduler_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 "content/renderer/scheduler/webthread_impl_for_renderer_scheduler.h"
+#include "content/renderer/scheduler/webthread_impl_for_scheduler.h"
 
 #include "base/run_loop.h"
 #include "content/child/scheduler/scheduler_message_loop_delegate.h"
@@ -28,14 +28,14 @@ class MockTaskObserver : public blink::WebThread::TaskObserver {
 };
 }  // namespace
 
-class WebThreadImplForRendererSchedulerTest : public testing::Test {
+class WebThreadImplForSchedulerTest : public testing::Test {
  public:
-  WebThreadImplForRendererSchedulerTest()
+  WebThreadImplForSchedulerTest()
       : scheduler_(SchedulerMessageLoopDelegate::Create(&message_loop_)),
         default_task_runner_(scheduler_.DefaultTaskRunner()),
         thread_(&scheduler_) {}
 
-  ~WebThreadImplForRendererSchedulerTest() override {}
+  ~WebThreadImplForSchedulerTest() override {}
 
   void SetWorkBatchSizeForTesting(size_t work_batch_size) {
     scheduler_.SetWorkBatchSizeForTesting(work_batch_size);
@@ -51,12 +51,12 @@ class WebThreadImplForRendererSchedulerTest : public testing::Test {
   base::MessageLoop message_loop_;
   RendererSchedulerImpl scheduler_;
   scoped_refptr<base::SingleThreadTaskRunner> default_task_runner_;
-  WebThreadImplForRendererScheduler thread_;
+  WebThreadImplForScheduler thread_;
 
-  DISALLOW_COPY_AND_ASSIGN(WebThreadImplForRendererSchedulerTest);
+  DISALLOW_COPY_AND_ASSIGN(WebThreadImplForSchedulerTest);
 };
 
-TEST_F(WebThreadImplForRendererSchedulerTest, TestTaskObserver) {
+TEST_F(WebThreadImplForSchedulerTest, TestTaskObserver) {
   MockTaskObserver observer;
   thread_.addTaskObserver(&observer);
   scoped_ptr<MockTask> task(new MockTask());
@@ -75,7 +75,7 @@ TEST_F(WebThreadImplForRendererSchedulerTest, TestTaskObserver) {
   thread_.removeTaskObserver(&observer);
 }
 
-TEST_F(WebThreadImplForRendererSchedulerTest, TestWorkBatchWithOneTask) {
+TEST_F(WebThreadImplForSchedulerTest, TestWorkBatchWithOneTask) {
   MockTaskObserver observer;
   thread_.addTaskObserver(&observer);
   scoped_ptr<MockTask> task(new MockTask());
@@ -95,7 +95,7 @@ TEST_F(WebThreadImplForRendererSchedulerTest, TestWorkBatchWithOneTask) {
   thread_.removeTaskObserver(&observer);
 }
 
-TEST_F(WebThreadImplForRendererSchedulerTest, TestWorkBatchWithTwoTasks) {
+TEST_F(WebThreadImplForSchedulerTest, TestWorkBatchWithTwoTasks) {
   MockTaskObserver observer;
   thread_.addTaskObserver(&observer);
   scoped_ptr<MockTask> task1(new MockTask());
@@ -121,7 +121,7 @@ TEST_F(WebThreadImplForRendererSchedulerTest, TestWorkBatchWithTwoTasks) {
   thread_.removeTaskObserver(&observer);
 }
 
-TEST_F(WebThreadImplForRendererSchedulerTest, TestWorkBatchWithThreeTasks) {
+TEST_F(WebThreadImplForSchedulerTest, TestWorkBatchWithThreeTasks) {
   MockTaskObserver observer;
   thread_.addTaskObserver(&observer);
   scoped_ptr<MockTask> task1(new MockTask());
@@ -172,7 +172,7 @@ void EnterRunLoop(base::MessageLoop* message_loop, blink::WebThread* thread) {
   run_loop.Run();
 }
 
-TEST_F(WebThreadImplForRendererSchedulerTest, TestNestedRunLoop) {
+TEST_F(WebThreadImplForSchedulerTest, TestNestedRunLoop) {
   MockTaskObserver observer;
   thread_.addTaskObserver(&observer);