Revert of Sketch DM refactor.

dm/DMTaskRunner.h

Index: dm/DMTaskRunner.h
diff --git a/dm/DMTaskRunner.h b/dm/DMTaskRunner.h
new file mode 100644
index 0000000000000000000000000000000000000000..3d4e491b9cb298becb4a30a40462cca1b23f28ac
--- /dev/null
+++ b/dm/DMTaskRunner.h
@@ -0,0 +1,29 @@
+#ifndef DMTaskRunner_DEFINED
+#define DMTaskRunner_DEFINED
+
+#include "DMGpuSupport.h"
+#include "SkTDArray.h"
+#include "SkTaskGroup.h"
+#include "SkTypes.h"
+
+namespace DM {
+
+class CpuTask;
+class GpuTask;
+
+class TaskRunner : SkNoncopyable {
+public:
+    TaskRunner() {}
+
+    void add(CpuTask* task);
+    void add(GpuTask* task);
+    void wait();
+
+private:
+    SkTaskGroup fCpuWork;
+    SkTDArray<GpuTask*> fGpuWork;
+};
+
+}  // namespace DM
+
+#endif  // DMTaskRunner_DEFINED