Revert of cc: Remove WorkerPool class and instead use TaskGraphRunner directly.

cc/resources/task_graph_runner.h

Index: cc/resources/task_graph_runner.h
diff --git a/cc/resources/task_graph_runner.h b/cc/resources/task_graph_runner.h
deleted file mode 100755
index 6915c5bb2785cc36c2db2f88aa40e76e1ecde94a..0000000000000000000000000000000000000000
--- a/cc/resources/task_graph_runner.h
+++ /dev/null
@@ -1,235 +0,0 @@
-// Copyright 2013 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 CC_RESOURCES_TASK_GRAPH_RUNNER_H_
-#define CC_RESOURCES_TASK_GRAPH_RUNNER_H_
-
-#include <queue>
-#include <string>
-#include <vector>
-
-#include "base/containers/scoped_ptr_hash_map.h"
-#include "base/memory/ref_counted.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/synchronization/condition_variable.h"
-#include "base/threading/simple_thread.h"
-#include "cc/base/cc_export.h"
-#include "cc/base/scoped_ptr_deque.h"
-
-namespace cc {
-namespace internal {
-
-class CC_EXPORT Task : public base::RefCountedThreadSafe<Task> {
- public:
-  typedef std::vector<scoped_refptr<Task> > Vector;
-
-  virtual void RunOnWorkerThread(unsigned thread_index) = 0;
-
-  void DidSchedule();
-  void WillRun();
-  void DidRun();
-
-  bool HasFinishedRunning() const;
-
- protected:
-  friend class base::RefCountedThreadSafe<Task>;
-
-  Task();
-  virtual ~Task();
-
-  bool did_schedule_;
-  bool did_run_;
-};
-
-}  // namespace internal
-}  // namespace cc
-
-#if defined(COMPILER_GCC)
-namespace BASE_HASH_NAMESPACE {
-template <> struct hash<cc::internal::Task*> {
-  size_t operator()(cc::internal::Task* ptr) const {
-    return hash<size_t>()(reinterpret_cast<size_t>(ptr));
-  }
-};
-}  // namespace BASE_HASH_NAMESPACE
-#endif  // COMPILER
-
-namespace cc {
-namespace internal {
-
-// Dependencies are represented by edges in a task graph. A graph node
-// store edges as a vector of dependents. Each graph node is assigned
-// a priority and a run count that matches the number of dependencies.
-class CC_EXPORT GraphNode {
- public:
-  typedef std::vector<GraphNode*> Vector;
-  typedef base::ScopedPtrHashMap<Task*, GraphNode> Map;
-
-  GraphNode(Task* task, unsigned priority);
-  ~GraphNode();
-
-  Task* task() { return task_; }
-
-  void add_dependent(GraphNode* dependent) {
-    DCHECK(dependent);
-    dependents_.push_back(dependent);
-  }
-  const Vector& dependents() const { return dependents_; }
-
-  unsigned priority() const { return priority_; }
-
-  unsigned num_dependencies() const { return num_dependencies_; }
-  void add_dependency() { ++num_dependencies_; }
-  void remove_dependency() {
-    DCHECK(num_dependencies_);
-    --num_dependencies_;
-  }
-
- private:
-  Task* task_;
-  Vector dependents_;
-  unsigned priority_;
-  unsigned num_dependencies_;
-
-  DISALLOW_COPY_AND_ASSIGN(GraphNode);
-};
-
-class TaskGraphRunner;
-
-// Opaque identifier that defines a namespace of tasks.
-class CC_EXPORT NamespaceToken {
- public:
-  NamespaceToken() : id_(0) {}
-  ~NamespaceToken() {}
-
-  bool IsValid() const {
-    return id_ != 0;
-  }
-
- private:
-  friend class TaskGraphRunner;
-
-  explicit NamespaceToken(int id) : id_(id) {}
-
-  int id_;
-};
-
-// A worker thread pool that runs tasks provided by task graph. Destructor
-// might block and should not be used on a thread that needs to be responsive.
-class CC_EXPORT TaskGraphRunner : public base::DelegateSimpleThread::Delegate {
- public:
-  typedef GraphNode::Map TaskGraph;
-
-  TaskGraphRunner(size_t num_threads, const std::string& thread_name_prefix);
-  virtual ~TaskGraphRunner();
-
-  // Returns a unique token that can be used to pass a task graph to
-  // SetTaskGraph(). Valid tokens are always nonzero.
-  NamespaceToken GetNamespaceToken();
-
-  // Schedule running of tasks in |graph|. Tasks previously scheduled but
-  // no longer needed will be canceled unless already running. Canceled
-  // tasks are moved to |completed_tasks| without being run. The result
-  // is that once scheduled, a task is guaranteed to end up in the
-  // |completed_tasks| queue even if it later get canceled by another
-  // call to SetTaskGraph().
-  void SetTaskGraph(NamespaceToken token, TaskGraph* graph);
-
-  // Wait for all scheduled tasks to finish running.
-  void WaitForTasksToFinishRunning(NamespaceToken token);
-
-  // Collect all completed tasks in |completed_tasks|.
-  void CollectCompletedTasks(
-      NamespaceToken token, Task::Vector* completed_tasks);
-
- private:
-  struct TaskNamespace {
-    typedef std::vector<TaskNamespace*> Vector;
-
-    TaskNamespace();
-    ~TaskNamespace();
-
-    // This set contains all pending tasks.
-    TaskGraph pending_tasks;
-    // This set contains all currently running tasks.
-    TaskGraph running_tasks;
-    // Completed tasks not yet collected by origin thread.
-    Task::Vector completed_tasks;
-    // Ordered set of tasks that are ready to run.
-    internal::GraphNode::Vector ready_to_run_tasks;
-  };
-
-  typedef base::ScopedPtrHashMap<int, TaskNamespace> TaskNamespaceMap;
-
-  static bool CompareTaskPriority(const internal::GraphNode* a,
-                                  const internal::GraphNode* b) {
-    // In this system, numerically lower priority is run first.
-    if (a->priority() != b->priority())
-      return a->priority() > b->priority();
-
-    // Run task with most dependents first when priority is the same.
-    return a->dependents().size() < b->dependents().size();
-  }
-
-  static bool CompareTaskNamespacePriority(const TaskNamespace* a,
-                                           const TaskNamespace* b) {
-    DCHECK(!a->ready_to_run_tasks.empty());
-    DCHECK(!b->ready_to_run_tasks.empty());
-
-    // Compare based on task priority of the ready_to_run_tasks heap
-    // .front() will hold the max element of the heap,
-    // except after pop_heap, when max element is moved to .back().
-    return CompareTaskPriority(a->ready_to_run_tasks.front(),
-                               b->ready_to_run_tasks.front());
-  }
-
-  static bool HasFinishedRunningTasksInNamespace(
-      TaskNamespace* task_namespace) {
-    return task_namespace->pending_tasks.empty() &&
-           task_namespace->running_tasks.empty();
-  }
-
-  // Overridden from base::DelegateSimpleThread:
-  virtual void Run() OVERRIDE;
-
-  // This lock protects all members of this class. Do not read or modify
-  // anything without holding this lock. Do not block while holding this
-  // lock.
-  mutable base::Lock lock_;
-
-  // Condition variable that is waited on by worker threads until new
-  // tasks are ready to run or shutdown starts.
-  base::ConditionVariable has_ready_to_run_tasks_cv_;
-
-  // Condition variable that is waited on by origin threads until a
-  // namespace has finished running all associated tasks.
-  base::ConditionVariable has_namespaces_with_finished_running_tasks_cv_;
-
-  // Provides a unique id to each NamespaceToken.
-  int next_namespace_id_;
-
-  // This set contains all namespaces with pending, running or completed
-  // tasks not yet collected.
-  TaskNamespaceMap namespaces_;
-
-  // Ordered set of task namespaces that have ready to run tasks.
-  TaskNamespace::Vector ready_to_run_namespaces_;
-
-  // Provides each running thread loop with a unique index. First thread
-  // loop index is 0.
-  unsigned next_thread_index_;
-
-  // Set during shutdown. Tells workers to exit when no more tasks
-  // are pending.
-  bool shutdown_;
-
-  ScopedPtrDeque<base::DelegateSimpleThread> workers_;
-
-  DISALLOW_COPY_AND_ASSIGN(TaskGraphRunner);
-};
-
-}  // namespace internal
-}  // namespace cc
-
-#endif  // CC_RESOURCES_TASK_GRAPH_RUNNER_H_