DM: write failed comparison mode .pngs one more level deep in the tree.

dm/DMWriteTask.h

 #ifndef DMWriteTask_DEFINED
 #define DMWriteTask_DEFINED
 
 #include "DMTask.h"
 #include "SkBitmap.h"
 #include "SkString.h"
+#include "SkTArray.h"
 
 // Writes a bitmap to a file.
 
 namespace DM {
 
 class WriteTask : public Task {
 
 public:
-    WriteTask(const Task& parent, SkBitmap bitmap);
+    WriteTask(const Task& parent,  // WriteTask must be a child Task.  Pass its parent here.
+              SkBitmap bitmap);    // Bitmap to write.
 
     virtual void draw() SK_OVERRIDE;
     virtual bool usesGpu() const SK_OVERRIDE { return false; }
     virtual bool shouldSkip() const SK_OVERRIDE;
     virtual SkString name() const SK_OVERRIDE;
 
 private:
-    SkString fConfig;
+    SkTArray<SkString> fSuffixes;
     SkString fGmName;
     const SkBitmap fBitmap;
+
+    void makeDirOrFail(SkString dir);
 };
 
 }  // namespace DM
 
 #endif  // DMWriteTask_DEFINED