Add "sample locations" feature to GrProcessor

src/gpu/GrTest.cpp

Index: src/gpu/GrTest.cpp
diff --git a/src/gpu/GrTest.cpp b/src/gpu/GrTest.cpp
index 9a37f2b82fb764c828fa1854e9913098e61bbd50..7aea22c41d4e3ac5c6754a2315735d88ec4714c2 100644
--- a/src/gpu/GrTest.cpp
+++ b/src/gpu/GrTest.cpp
@@ -316,6 +316,13 @@ public:
                        const SkIRect& srcRect,
                        const SkIPoint& dstPoint) override { return false; };
 
+    void onGetMultisampleSpecs(GrRenderTarget* rt,
+                               const GrStencilSettings&,
+                               int* effectiveSampleCnt,
+                               SamplePattern*) override {
+        *effectiveSampleCnt = rt->desc().fSampleCnt;
+    }
+
     bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) const override {
         return false;
     }