DM: make GPU tasks multithreaded again. Big refactor.

dm/DMReplayTask.cpp

 #include "DMReplayTask.h"
 #include "DMWriteTask.h"
 #include "DMUtil.h"
 
 #include "SkCommandLineFlags.h"
 #include "SkPicture.h"
 
 DEFINE_bool(replay, true, "If true, run picture replay tests.");
 DEFINE_bool(rtree,  true, "If true, run picture replay tests with an rtree.");
 
 namespace DM {
 
 ReplayTask::ReplayTask(const Task& parent,
                        skiagm::GM* gm,
                        SkBitmap reference,
                        bool useRTree)
-    : Task(parent)
+    : CpuTask(parent)
     , fName(UnderJoin(parent.name().c_str(), useRTree ? "rtree" : "replay"))
     , fGM(gm)
     , fReference(reference)
     , fUseRTree(useRTree)
     {}
 
 void ReplayTask::draw() {
     SkPicture recorded;
     const uint32_t flags = fUseRTree ? SkPicture::kOptimizeForClippedPlayback_RecordingFlag : 0;
     RecordPicture(fGM.get(), &recorded, flags);
@@ skipping 15 matching lines @@
     if (FLAGS_rtree && fUseRTree) {
         return (fGM->getFlags() & skiagm::GM::kSkipTiled_Flag) != 0;
     }
     if (FLAGS_replay && !fUseRTree) {
         return false;
     }
     return true;
 }
 
 }  // namespace DM