Move thread_pool.h into utils so it can be shared by more than one example.

native_client_sdk/src/examples/demo/voronoi/voronoi.cc

 // Copyright (c) 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.
 
 #include <assert.h>
 #include <math.h>
 #include <ppapi/cpp/completion_callback.h>
 #include <ppapi/cpp/graphics_2d.h>
 #include <ppapi/cpp/image_data.h>
 #include <ppapi/cpp/input_event.h>
 #include <ppapi/cpp/instance.h>
 #include <ppapi/cpp/module.h>
 #include <ppapi/cpp/rect.h>
 #include <ppapi/cpp/size.h>
 #include <ppapi/cpp/var.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/time.h>
 #include <unistd.h>
 
 #include <algorithm>
 #include <string>
 
-#include "threadpool.h"
+#include "sdk_util/thread_pool.h"
 
 // Global properties used to setup Voronoi demo.
 namespace {
 const int kMinRectSize = 4;
 const int kStartRecurseSize = 32;  // must be power-of-two
 const float kHugeZ = 1.0e38f;
 const float kPI = M_PI;
 const float kTwoPI = kPI * 2.0f;
 const int kFramesToBenchmark = 100;
 const unsigned int kRandomStartSeed = 0xC0DE533D;
@@ skipping 536 matching lines @@
     return new Voronoi(instance);
   }
 };
 
 namespace pp {
 Module* CreateModule() {
   return new VoronoiModule();
 }
 }  // namespace pp