Add discard support to Vulkan

src/gpu/vk/GrVkCaps.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrVkCaps.h"
 
 #include "GrVkUtil.h"
 #include "glsl/GrGLSLCaps.h"
 #include "vk/GrVkInterface.h"
 #include "vk/GrVkBackendContext.h"
 
 GrVkCaps::GrVkCaps(const GrContextOptions& contextOptions, const GrVkInterface* vkInterface,
                    VkPhysicalDevice physDev, uint32_t featureFlags, uint32_t extensionFlags)
     : INHERITED(contextOptions) {
     fCanUseGLSLForShaderModule = false;
 
     /**************************************************************************
     * GrDrawTargetCaps fields
     **************************************************************************/
     fMipMapSupport = true;   // always available in Vulkan
     fSRGBSupport = true;   // always available in Vulkan
     fNPOTTextureTileSupport = true;  // always available in Vulkan
     fTwoSidedStencilSupport = true;  // always available in Vulkan
     fStencilWrapOpsSupport = true; // always available in Vulkan
-    fDiscardRenderTargetSupport = false; //TODO: figure this out
+    fDiscardRenderTargetSupport = true;
     fReuseScratchTextures = true; //TODO: figure this out
     fGpuTracingSupport = false; //TODO: figure this out
     fCompressedTexSubImageSupport = false; //TODO: figure this out
     fOversizedStencilSupport = false; //TODO: figure this out
 
     fUseDrawInsteadOfClear = false;
 
     fMapBufferFlags = kNone_MapFlags; //TODO: figure this out
     fBufferMapThreshold = SK_MaxS32;  //TODO: figure this out
 
@@ skipping 198 matching lines @@
 
 void GrVkCaps::ConfigInfo::init(const GrVkInterface* interface,
                                 VkPhysicalDevice physDev,
                                 VkFormat format) {
     VkFormatProperties props;
     memset(&props, 0, sizeof(VkFormatProperties));
     GR_VK_CALL(interface, GetPhysicalDeviceFormatProperties(physDev, format, &props));
     InitConfigFlags(props.linearTilingFeatures, &fLinearFlags);
     InitConfigFlags(props.optimalTilingFeatures, &fOptimalFlags);
 }