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

cc/resources/picture_pile.cc

Index: cc/resources/picture_pile.cc
diff --git a/cc/resources/picture_pile.cc b/cc/resources/picture_pile.cc
index 443f8be9aaf001ed6ef2d238d51404c098ab4dbb..d5928a497fbc85d48cd23590f7b1657d758cb932 100644
--- a/cc/resources/picture_pile.cc
+++ b/cc/resources/picture_pile.cc
@@ -11,8 +11,8 @@
 #include "cc/base/region.h"
 #include "cc/debug/rendering_stats_instrumentation.h"
 #include "cc/resources/picture_pile_impl.h"
-#include "cc/resources/raster_worker_pool.h"
 #include "cc/resources/tile_priority.h"
+#include "cc/resources/worker_pool.h"
 
 namespace {
 // Layout pixel buffer around the visible layer rect to record.  Any base
@@ -232,7 +232,7 @@
       }
       int recorded_pixel_count =
           picture->LayerRect().width() * picture->LayerRect().height();
-      int num_raster_threads = RasterWorkerPool::GetNumRasterThreads();
+      int num_raster_threads = WorkerPool::GetNumRasterThreads();
       stats_instrumentation->AddRecord(best_duration, recorded_pixel_count);
       if (num_raster_threads > 1)
         picture->GatherPixelRefs(tile_grid_info_);