Re-land: cc: Remove WorkerPool class and instead use TaskGraphRunner directly.

cc/base/switches.cc

Index: cc/base/switches.cc
diff --git a/cc/base/switches.cc b/cc/base/switches.cc
index 5f405ea082e334350f478c042d2b920c447000f9..487c5ec296bdf9158605d6347dc05d21ec882d18 100644
--- a/cc/base/switches.cc
+++ b/cc/base/switches.cc
@@ -54,9 +54,6 @@ const char kTopControlsHideThreshold[] = "top-controls-hide-threshold";
 // Percentage of the top controls need to be shown before they will auto show.
 const char kTopControlsShowThreshold[] = "top-controls-show-threshold";
 
-// Number of worker threads used to rasterize content.
-const char kNumRasterThreads[] = "num-raster-threads";
-
 // Show metrics about overdraw in about:tracing recordings, such as the number
 // of pixels culled, and the number of pixels drawn, for each frame.
 const char kTraceOverdraw[] = "trace-overdraw";