Revert of SkThreadPool ~~> SkTaskGroup

dm/DMTestTask.h

 #ifndef DMTestTask_DEFINED
 #define DMTestTask_DEFINED
 
 #include "DMReporter.h"
 #include "DMTask.h"
 #include "DMTaskRunner.h"
 #include "SkString.h"
 #include "SkTemplates.h"
 #include "Test.h"
 
 // Runs a unit test.
 namespace DM {
 
 class TestReporter : public skiatest::Reporter {
 public:
   TestReporter() {}
 
   const char* failure() const { return fFailure.c_str(); }
 
 private:
   virtual bool allowExtendedTest() const SK_OVERRIDE;
+  virtual bool allowThreaded()     const SK_OVERRIDE;
   virtual bool verbose()           const SK_OVERRIDE;
 
   virtual void onReportFailed(const SkString& desc) SK_OVERRIDE {
       fFailure = desc;
   }
 
   SkString fFailure;
 };
 
 class CpuTestTask : public CpuTask {
@@ skipping 20 matching lines @@
 
 private:
     TestReporter fTestReporter;
     SkAutoTDelete<skiatest::Test> fTest;
     const SkString fName;
 };
 
 }  // namespace DM
 
 #endif // DMTestTask_DEFINED