Update DM JSON format.

dm/DMSKPTask.cpp

 #include "DMSKPTask.h"
 #include "DMUtil.h"
 #include "DMWriteTask.h"
 
 #include "SkCommandLineFlags.h"
 #include "SkPictureRecorder.h"
 
 DEFINE_int32(skpMaxWidth,  1000, "Max SKPTask viewport width.");
 DEFINE_int32(skpMaxHeight, 1000, "Max SKPTask viewport height.");
 
 namespace DM {
 
 SKPTask::SKPTask(Reporter* r,
                  TaskRunner* tr,
                  const SkPicture* pic,
                  SkString filename)
     : CpuTask(r, tr)
     , fPicture(SkRef(pic))
     , fName(FileToTaskName(filename)) {}
 
 void SKPTask::draw() {
     const int width  = SkTMin(SkScalarCeilToInt(fPicture->cullRect().width()),  FLAGS_skpMaxWidth),
               height = SkTMin(SkScalarCeilToInt(fPicture->cullRect().height()), FLAGS_skpMaxHeight);
     SkBitmap bitmap;
     AllocatePixels(kN32_SkColorType, width, height, &bitmap);
     DrawPicture(*fPicture, &bitmap);
 
-    this->spawnChild(SkNEW_ARGS(WriteTask, (*this, bitmap)));
+    this->spawnChild(SkNEW_ARGS(WriteTask, (*this, "SKP", bitmap)));
 }
 
 }  // namespace DM