Add option to draw wireframe batch bounds

src/gpu/GrGpu.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGpu_DEFINED
 #define GrGpu_DEFINED
 
@@ skipping 369 matching lines @@
 
     // width and height may be larger than rt (if underlying API allows it).
     // Returns nullptr if compatible sb could not be created, otherwise the caller owns the ref on
     // the GrStencilAttachment.
     virtual GrStencilAttachment* createStencilAttachmentForRenderTarget(const GrRenderTarget*,
                                                                         int width,
                                                                         int height) = 0;
     // clears target's entire stencil buffer to 0
     virtual void clearStencil(GrRenderTarget* target) = 0;
 
+    // draws an outline rectangle for debugging/visualization purposes.
+    virtual void drawDebugWireRect(GrRenderTarget*, const SkIRect&, GrColor) = 0;
 
     // Determines whether a copy of a texture must be made in order to be compatible with
     // a given GrTextureParams. If so, the width, height and filter used for the copy are
     // output via the CopyParams.
     bool makeCopyForTextureParams(int width, int height, const GrTextureParams&,
                                   GrTextureProducer::CopyParams*) const;
 
     // This is only to be used in GL-specific tests.
     virtual const GrGLContext* glContextForTesting() const { return nullptr; }
 
@@ skipping 106 matching lines @@
     ResetTimestamp                                                      fResetTimestamp;
     uint32_t                                                            fResetBits;
     // The context owns us, not vice-versa, so this ptr is not ref'ed by Gpu.
     GrContext*                                                          fContext;
 
     friend class GrPathRendering;
     typedef SkRefCnt INHERITED;
 };
 
 #endif