Add debugging helper to GrDrawTarget

src/gpu/GrDrawTarget.h

Index: src/gpu/GrDrawTarget.h
diff --git a/src/gpu/GrDrawTarget.h b/src/gpu/GrDrawTarget.h
index 925c03e741080a5f7cdebc51a8c32587b26146c4..ec94da1f0e72f2351566979fac9d17c9f4211fe2 100644
--- a/src/gpu/GrDrawTarget.h
+++ b/src/gpu/GrDrawTarget.h
@@ -70,6 +70,11 @@ public:
         return fDependencies.find(dependedOn) >= 0;
     }
 
+    /*
+     * Dump out the drawTarget dependency DAG
+     */
+    SkDEBUGCODE(void dump() const;)
+
     /**
      * Empties the draw buffer of any queued up draws.
      */
@@ -304,6 +309,7 @@ private:
     bool                                        fFlushing;
     int                                         fFirstUnpreparedBatch;
 
+    SkDEBUGCODE(int                             fDebugID;)
     uint32_t                                    fFlags;
 
     // 'this' drawTarget relies on the output of the drawTargets in 'fDependencies'