Add "sample locations" feature to GrProcessor

src/gpu/gl/GrGLProgramDesc.cpp

Index: src/gpu/gl/GrGLProgramDesc.cpp
diff --git a/src/gpu/gl/GrGLProgramDesc.cpp b/src/gpu/gl/GrGLProgramDesc.cpp
index 789eb6233605fa1de22e288f898e77703aa87858..485e90be8aec3411fdfc6703141a7fbb72b32e4a 100644
--- a/src/gpu/gl/GrGLProgramDesc.cpp
+++ b/src/gpu/gl/GrGLProgramDesc.cpp
@@ -147,15 +147,15 @@ bool GrGLProgramDescBuilder::Build(GrProgramDesc* desc,
     // make sure any padding in the header is zeroed.
     memset(header, 0, kHeaderSize);
 
+    GrRenderTarget* rt = pipeline.getRenderTarget();
+
     if (requiredFeatures & GrProcessor::kFragmentPosition_RequiredFeature) {
-        header->fFragPosKey =
-                GrGLSLFragmentShaderBuilder::KeyForFragmentPosition(pipeline.getRenderTarget());
+        header->fFragPosKey = GrGLSLFragmentShaderBuilder::KeyForFragmentPosition(rt);
     } else {
         header->fFragPosKey = 0;
     }
 
-    header->fOutputSwizzle =
-        glslCaps.configOutputSwizzle(pipeline.getRenderTarget()->config()).asKey();
+    header->fOutputSwizzle = glslCaps.configOutputSwizzle(rt->config()).asKey();
 
     if (pipeline.ignoresCoverage()) {
         header->fIgnoresCoverage = 1;
@@ -166,6 +166,15 @@ bool GrGLProgramDescBuilder::Build(GrProgramDesc* desc,
     header->fSnapVerticesToPixelCenters = pipeline.snapVerticesToPixelCenters();
     header->fColorEffectCnt = pipeline.numColorFragmentProcessors();
     header->fCoverageEffectCnt = pipeline.numCoverageFragmentProcessors();
+
+    if (requiredFeatures & GrProcessor::kSampleLocations_RequiredFeature) {
+        SkASSERT(pipeline.isHWAntialiasState());
+        header->fSamplePatternKey =
+            rt->renderTargetPriv().getSamplePatternID(pipeline.getStencil());
+    } else {
+        header->fSamplePatternKey = 0;
+    }
+
     glDesc->finalize();
     return true;
 }