Replace fWillReadFragmentPosition with a bitfield

src/gpu/vk/GrVkProgramDesc.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 "GrVkProgramDesc.h"
 
 //#include "GrVkProcessor.h"
 #include "GrProcessor.h"
@@ skipping 89 matching lines @@
     vkDesc->key().reset();
     vkDesc->key().push_back_n(kProcessorKeysOffset);
 
     GrProcessorKeyBuilder b(&vkDesc->key());
 
     primProc.getGLSLProcessorKey(glslCaps, &b);
     if (!gen_meta_key(primProc, glslCaps, 0, &b)) {
         vkDesc->key().reset();
         return false;
     }
+    GrProcessor::RequiredFeatures requiredFeatures = primProc.requiredFeatures();
 
     for (int i = 0; i < pipeline.numFragmentProcessors(); ++i) {
         const GrFragmentProcessor& fp = pipeline.getFragmentProcessor(i);
         if (!gen_frag_proc_and_meta_keys(primProc, fp, glslCaps, &b)) {
             vkDesc->key().reset();
             return false;
         }
+        requiredFeatures |= fp.requiredFeatures();
     }
 
     const GrXferProcessor& xp = pipeline.getXferProcessor();
     xp.getGLSLProcessorKey(glslCaps, &b);
     if (!gen_meta_key(xp, glslCaps, 0, &b)) {
         vkDesc->key().reset();
         return false;
     }
+    requiredFeatures |= xp.requiredFeatures();
 
     // --------DO NOT MOVE HEADER ABOVE THIS LINE--------------------------------------------------
     // Because header is a pointer into the dynamic array, we can't push any new data into the key
     // below here.
     KeyHeader* header = vkDesc->atOffset<KeyHeader, kHeaderOffset>();
 
     // make sure any padding in the header is zeroed.
     memset(header, 0, kHeaderSize);
 
-    if (pipeline.readsFragPosition()) {
+    if (requiredFeatures & GrProcessor::kFragmentPosition_RequiredFeature) {
         header->fFragPosKey =
             GrGLSLFragmentShaderBuilder::KeyForFragmentPosition(pipeline.getRenderTarget());
     } else {
         header->fFragPosKey = 0;
     }
 
     header->fOutputSwizzle =
         glslCaps.configOutputSwizzle(pipeline.getRenderTarget()->config()).asKey();
 
     if (pipeline.ignoresCoverage()) {
         header->fIgnoresCoverage = 1;
     } else {
         header->fIgnoresCoverage = 0;
     }
 
     header->fSnapVerticesToPixelCenters = pipeline.snapVerticesToPixelCenters();
     header->fColorEffectCnt = pipeline.numColorFragmentProcessors();
     header->fCoverageEffectCnt = pipeline.numCoverageFragmentProcessors();
     vkDesc->finalize();
     return true;
 }