Add "sample locations" feature to GrProcessor

src/gpu/GrPipelineBuilder.h

Index: src/gpu/GrPipelineBuilder.h
diff --git a/src/gpu/GrPipelineBuilder.h b/src/gpu/GrPipelineBuilder.h
index f5fe9f80dc38196d583183845a0990684b88eced..ea84c2565558f478b61954155415b794dc2c8daf 100644
--- a/src/gpu/GrPipelineBuilder.h
+++ b/src/gpu/GrPipelineBuilder.h
@@ -291,12 +291,19 @@ public:
          */
         kSnapVerticesToPixelCenters_Flag = 0x02,
 
-        kLast_Flag = kSnapVerticesToPixelCenters_Flag,
+        /**
+         * Adds built-in information about sample locations to the fragment shader. Requires HW
+         * antialias and support for sample locations in the caps.
+         */
+        kSampleLocations_Flag = 0x04,
+
+        kLast_Flag = kSampleLocations_Flag,
     };
 
     bool isHWAntialias() const { return SkToBool(fFlags & kHWAntialias_Flag); }
     bool snapVerticesToPixelCenters() const {
         return SkToBool(fFlags & kSnapVerticesToPixelCenters_Flag); }
+    bool hasSampleLocations() const { return SkToBool(fFlags & kSampleLocations_Flag); }
 
     /**
      * Enable render state settings.