Update Vulkan docs

include/gpu/GrTypes.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrTypes_DEFINED
 #define GrTypes_DEFINED
 
@@ skipping 124 matching lines @@
     kOpenGL_GrBackend,
     kVulkan_GrBackend,
 
     kLast_GrBackend = kVulkan_GrBackend
 };
 const int kBackendCount = kLast_GrBackend + 1;
 
 /**
  * Backend-specific 3D context handle
  *      GrGLInterface* for OpenGL. If NULL will use the default GL interface.
+ *      GrVkBackendContext* for Vulkan.
  */
 typedef intptr_t GrBackendContext;
 
 ///////////////////////////////////////////////////////////////////////////////
 
 /**
 * Geometric primitives used for drawing.
 */
 enum GrPrimitiveType {
     kTriangles_GrPrimitiveType,
@@ skipping 407 matching lines @@
     int                             fHeight;        //<! height in pixels
     GrPixelConfig                   fConfig;        //<! color format
     /**
      * If the render target flag is set and sample count is greater than 0
      * then Gr will create an MSAA buffer that resolves to the texture.
      */
     int                             fSampleCnt;
     /**
      * Handle to the 3D API object.
      * OpenGL: Texture ID.
+     * Vulkan: GrVkImageInfo*
      */
     GrBackendObject                 fTextureHandle;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 /**
  * Gr can wrap an existing render target created by the client in the 3D API
  * with a GrRenderTarget object. The client is responsible for ensuring that the
  * underlying 3D API object lives at least as long as the GrRenderTarget object
@@ skipping 14 matching lines @@
      * about applying other forms of anti-aliasing.
      */
     int                             fSampleCnt;
     /**
      * Number of bits of stencil per-pixel.
      */
     int                             fStencilBits;
     /**
      * Handle to the 3D API object.
      * OpenGL: FBO ID
+     * Vulkan: GrVkImageInfo*
      */
     GrBackendObject                 fRenderTargetHandle;
 };
 
 /**
  * The GrContext's cache of backend context state can be partially invalidated.
  * These enums are specific to the GL backend and we'd add a new set for an alternative backend.
  */
 enum GrGLBackendState {
     kRenderTarget_GrGLBackendState     = 1 << 0,
@@ skipping 40 matching lines @@
             return 4 * width * height;
     }
 }
 
 /**
  * This value translates to reseting all the context state for any backend.
  */
 static const uint32_t kAll_GrBackendState = 0xffffffff;
 
 #endif