Add mixed samples support to XPs

src/gpu/GrPipelineBuilder.h

Index: src/gpu/GrPipelineBuilder.h
diff --git a/src/gpu/GrPipelineBuilder.h b/src/gpu/GrPipelineBuilder.h
index dbbf98a815a8dedfd418743b61814a3622baa101..6a0e137f99bb090eca89020bbba6b5b22dcf7961 100644
--- a/src/gpu/GrPipelineBuilder.h
+++ b/src/gpu/GrPipelineBuilder.h
@@ -205,6 +205,14 @@ public:
      */
     void setRenderTarget(GrRenderTarget* target) { fRenderTarget.reset(SkSafeRef(target)); }
 
+    /**
+     * Returns whether the rasterizer and stencil test (if any) will run at a higher sample rate
+     * than the color buffer. In is scenario, the higher sample rate is resolved during blending.
+     */
+    bool hasMixedSamples() const {
+        return this->isHWAntialias() && !fRenderTarget->isMultisampled();
+    }
+
     /// @}
 
     ///////////////////////////////////////////////////////////////////////////