Make GrCircleBlurFragmentProcessor::onIsEqual include the position

Previously we would fail to draw two adjacent blurred circles if they differed
only by their position.
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Review URL: https://codereview.chromium.org/1824693003

src/effects/GrCircleBlurFragmentProcessor.h

@@ -64,7 +64,7 @@ private:
     bool onIsEqual(const GrFragmentProcessor& other) const override {
         const GrCircleBlurFragmentProcessor& cbfp = other.cast<GrCircleBlurFragmentProcessor>();
         // fOffset is computed from the circle width and the sigma
-        return this->circle().width() == cbfp.circle().width() && fSigma == cbfp.fSigma;    
+        return this->circle() == cbfp.circle() && fSigma == cbfp.fSigma;
     }
 
     void onComputeInvariantOutput(GrInvariantOutput* inout) const override;