Put clear and discard into GrBatch.

src/gpu/batches/GrBatch.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrBatch_DEFINED
 #define GrBatch_DEFINED
 
 #include <new>
 #include "GrNonAtomicRef.h"
 
 #include "SkRect.h"
+#include "SkString.h"
 
 class GrCaps;
+class GrBatchFlushState;
 
 /**
  * GrBatch is the base class for all Ganesh deferred geometry generators.  To facilitate
  * reorderable batching, Ganesh does not generate geometry inline with draw calls.  Instead, it
  * captures the arguments to the draw and then generates the geometry on demand.  This gives GrBatch
  * subclasses complete freedom to decide how / what they can batch.
  *
  * Batches are created when GrContext processes a draw call. Batches of the same  subclass may be
  * merged using combineIfPossible. When two batches merge, one takes on the union of the data
  * and the other is left empty. The merged batch becomes responsible for drawing the data from both
@@ skipping 45 matching lines @@
     template <typename T> const T& cast() const { return *static_cast<const T*>(this); }
     template <typename T> T* cast() { return static_cast<T*>(this); }
 
     uint32_t classID() const { SkASSERT(kIllegalBatchID != fClassID); return fClassID; }
 
 #if GR_BATCH_SPEW
     uint32_t uniqueID() const { return fUniqueID; }
 #endif
     SkDEBUGCODE(bool isUsed() const { return fUsed; })
 
+    /** Called prior to drawing. The batch should perform any resource creation necessary to
+        to quickly issue its draw when draw is called. */
+    void prepare(GrBatchFlushState* state) { this->onPrepare(state); }
+
+    /** Issues the batches commands to GrGpu. */
+    void draw(GrBatchFlushState* state) { this->onDraw(state); }
+
+    /** Used to block batching across render target changes. Remove this once we store
+        GrBatches for different RTs in different targets. */
+    virtual uint32_t renderTargetUniqueID() const = 0;
+
+    /** Used for spewing information about batches when debugging. */
+    virtual SkString dumpInfo() const = 0;
+
 protected:
     template <typename PROC_SUBCLASS> void initClassID() {
          static uint32_t kClassID = GenID(&gCurrBatchClassID);
          fClassID = kClassID;
     }
 
     // NOTE, compute some bounds, even if extremely conservative.  Do *NOT* setLargest on the bounds
     // rect because we outset it for dst copy textures
     void setBounds(const SkRect& newBounds) { fBounds = newBounds; }
 
     void joinBounds(const SkRect& otherBounds) {
         return fBounds.joinPossiblyEmptyRect(otherBounds);
     }
 
     SkRect                              fBounds;
 
 private:
     virtual bool onCombineIfPossible(GrBatch*, const GrCaps& caps) = 0;
 
+    virtual void onPrepare(GrBatchFlushState*) = 0;
+    virtual void onDraw(GrBatchFlushState*) = 0;
+
     static uint32_t GenID(int32_t* idCounter) {
         // fCurrProcessorClassID has been initialized to kIllegalProcessorClassID. The
         // atomic inc returns the old value not the incremented value. So we add
         // 1 to the returned value.
         uint32_t id = static_cast<uint32_t>(sk_atomic_inc(idCounter)) + 1;
         if (!id) {
             SkFAIL("This should never wrap as it should only be called once for each GrBatch "
                    "subclass.");
         }
         return id;
     }
 
     enum {
         kIllegalBatchID = 0,
     };
 
     uint32_t                            fClassID;
     SkDEBUGCODE(bool                    fUsed;)
 #if GR_BATCH_SPEW
     uint32_t                            fUniqueID;
     static int32_t gCurrBatchUniqueID;
 #endif
     static int32_t gCurrBatchClassID;
     typedef GrNonAtomicRef INHERITED;
 };
 
 #endif