DM: add --rtree.

dm/DMReplayTask.h

 #ifndef DMReplayTask_DEFINED
 #define DMReplayTask_DEFINED
 
 #include "DMTask.h"
 #include "SkBitmap.h"
 #include "SkString.h"
 #include "SkTemplates.h"
 #include "gm.h"
 
 // Records a GM through an SkPicture, draws it, and compares against the reference bitmap.
 
 namespace DM {
 
 class ReplayTask : public Task {
 
 public:
-    ReplayTask(const Task& parent,
-               skiagm::GM*,
-               SkBitmap reference);
+    ReplayTask(const Task& parent,     // ReplayTask must be a child task.  Pass its parent here.
+               skiagm::GM*,            // GM to run through a pipe.  Takes ownership.
+               SkBitmap reference,     // Bitmap to compare pipe results to.
+               uint32_t recordFlags);  // Flags to pass to SkPicture::beginRecording().

[epoger, 2013/10/30 19:37:01]

AFAICT, there are exactly two allowed values to pass in recordFlags: 0 and
SkPicture::kOptimizeForClippedPlayback_RecordingFlag

I think developers will be rightfully confused.  "So, I can pass in any single
value in the SkPicture::RecordingFlags enum?  Or a bitmask of those values?"

 
     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 { return fName; }
 
 private:
     const SkString fName;
     SkAutoTDelete<skiagm::GM> fGM;
     const SkBitmap fReference;
+    const uint32_t fRecordFlags;
 };
 
 }  // namespace DM
 
 #endif  // DMReplayTask_DEFINED