Revert of SkThreadPool ~~> SkTaskGroup

tests/OnceTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkOnce.h"
-#include "SkTaskGroup.h"
+#include "SkThreadPool.h"
 #include "Test.h"
 
 static void add_five(int* x) {
     *x += 5;
 }
 
 DEF_TEST(SkOnce_Singlethreaded, r) {
     int x = 0;
 
     SK_DECLARE_STATIC_ONCE(once);
@@ skipping 15 matching lines @@
 public:
     SkOnceFlag* once;
     int* ptr;
 
     virtual void run() SK_OVERRIDE {
         SkOnce(once, add_six, ptr);
     }
 };
 
 DEF_TEST(SkOnce_Multithreaded, r) {
-    const int kTasks = 16;
+    const int kTasks = 16, kThreads = 4;
 
     // Make a bunch of tasks that will race to be the first to add six to x.
     Racer racers[kTasks];
     SK_DECLARE_STATIC_ONCE(once);
     int x = 0;
     for (int i = 0; i < kTasks; i++) {
         racers[i].once = &once;
         racers[i].ptr = &x;
     }
 
     // Let them race.
-    SkTaskGroup tg;
+    SkThreadPool pool(kThreads);
     for (int i = 0; i < kTasks; i++) {
-        tg.add(&racers[i]);
+        pool.add(&racers[i]);
     }
-    tg.wait();
+    pool.wait();
 
     // Only one should have done the +=.
     REPORTER_ASSERT(r, 6 == x);
 }
 
 static int gX = 0;
 static void inc_gX() { gX++; }
 
 DEF_TEST(SkOnce_NoArg, r) {
     SK_DECLARE_STATIC_ONCE(once);
     SkOnce(&once, inc_gX);
     SkOnce(&once, inc_gX);
     SkOnce(&once, inc_gX);
     REPORTER_ASSERT(r, 1 == gX);
 }