Move threadpool code from include/utils to tools/threadpool.

tools/threadpool/Runnable.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
-#ifndef SkRunnable_DEFINED
-#define SkRunnable_DEFINED
+#ifndef Runnable_DEFINED
+#define Runnable_DEFINED
 
 template <typename T>
-struct SkTRunnable {
-    virtual ~SkTRunnable() {};
+struct TRunnable {
+    virtual ~TRunnable() {};
     virtual void run(T&) = 0;
 };
 
 template <>
-struct SkTRunnable<void> {
-    virtual ~SkTRunnable() {};
+struct TRunnable<void> {
+    virtual ~TRunnable() {};
     virtual void run() = 0;
 };
 
-typedef SkTRunnable<void> SkRunnable;
+typedef TRunnable<void> Runnable;
 
 #endif