Convert GrClip to an abstract base class

include/gpu/GrTypesPriv.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrTypesPriv_DEFINED
 #define GrTypesPriv_DEFINED
 
@@ skipping 383 matching lines @@
  * Indicates the type of pending IO operations that can be recorded for gpu resources.
  */
 enum GrIOType {
     kRead_GrIOType,
     kWrite_GrIOType,
     kRW_GrIOType
 };
 
 struct GrScissorState {
     GrScissorState() : fEnabled(false) {}
+    GrScissorState(const SkIRect& rect) : fEnabled(true), fRect(rect) {}
+    void setDisabled() { fEnabled = false; }
     void set(const SkIRect& rect) { fRect = rect; fEnabled = true; }
     bool operator==(const GrScissorState& other) const {
         return fEnabled == other.fEnabled &&
                 (false == fEnabled || fRect == other.fRect);
     }
     bool operator!=(const GrScissorState& other) const { return !(*this == other); }
 
     bool enabled() const { return fEnabled; }
     const SkIRect& rect() const { return fRect; }
 
@@ skipping 54 matching lines @@
  * Specifies if the holder owns the backend, OpenGL or Vulkan, object.
  */
 enum class GrBackendObjectOwnership : bool {
     /** Holder does not destroy the backend object. */
     kBorrowed = false,
     /** Holder destroys the backend object. */
     kOwned = true
 };
 
 #endif