Add option to draw wireframe batch bounds

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 2d05396f87c8f71720b6b71837c533e0bfb2210a..c191f800cfbae5d8eb3b1d336155ef41eed2a2bd 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -130,6 +130,8 @@ public:
 
     void resetShaderCacheForTesting() const override;
 
+    void drawDebugWireRect(GrRenderTarget*, const SkIRect&, GrColor) override;
+
 private:
     GrGLGpu(GrGLContext* ctx, GrContext* context);
 
@@ -326,6 +328,8 @@ private:
     SkAutoTUnref<GrGLContext>  fGLContext;
 
     void createCopyPrograms();
+    void createWireRectProgram();
+    void createUnitRectBuffer();
 
     // GL program-related state
     ProgramCache*               fProgramCache;
@@ -503,6 +507,13 @@ private:
     }                           fCopyPrograms[2];
     GrGLuint                    fCopyProgramArrayBuffer;
 
+    struct {
+        GrGLuint fProgram;
+        GrGLint  fColorUniform;
+        GrGLint  fRectUniform;
+    }                           fWireRectProgram;
+    GrGLuint                    fWireRectArrayBuffer;
+
     static int TextureTargetToCopyProgramIdx(GrGLenum target) {
         if (target == GR_GL_TEXTURE_2D) {
             return 0;