Made shadows blurry (thru implementing variance mapping)

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2224163005

Review-Url: https://codereview.chromium.org/2224163005
diff --git a/src/core/SkShadowShader.h b/src/core/SkShadowShader.h
index 163d58a..3263950 100644
--- a/src/core/SkShadowShader.h
+++ b/src/core/SkShadowShader.h
@@ -23,7 +23,8 @@
     static sk_sp<SkShader> Make(sk_sp<SkShader> povDepthShader,
                                 sk_sp<SkShader> diffuseShader,
                                 sk_sp<SkLights> lights,
-                                int diffuseWidth, int diffuseHeight);
+                                int diffuseWidth, int diffuseHeight,
+                                const SkShadowParams& params);
 
     // The shadow shader supports any number of ambient lights, but only
     // 4 non-ambient lights (currently just refers to directional lights).