add asAShadowBlur for android to drawlooper

src/effects/SkBlurDrawLooper.cpp

Index: src/effects/SkBlurDrawLooper.cpp
diff --git a/src/effects/SkBlurDrawLooper.cpp b/src/effects/SkBlurDrawLooper.cpp
index 78506690a88d8efcae78dd82a5a441d6af2f62ac..6a6b9c04d78052d349b9bb32610b05c1a88e1284 100644
--- a/src/effects/SkBlurDrawLooper.cpp
+++ b/src/effects/SkBlurDrawLooper.cpp
@@ -33,6 +33,7 @@ void SkBlurDrawLooper::init(SkScalar sigma, SkScalar dx, SkScalar dy,
                             SkColor color, uint32_t flags) {
     fDx = dx;
     fDy = dy;
+    fSigma = sigma;
     fBlurColor = color;
     fBlurFlags = flags;
 
@@ -91,6 +92,21 @@ void SkBlurDrawLooper::flatten(SkWriteBuffer& buffer) const {
     buffer.writeUInt(fBlurFlags);
 }
 
+bool SkBlurDrawLooper::asABlurShadow(BlurShadowRec* rec) const {
+    if (fSigma <= 0.5f) {
+        return false;
+    }
+
+    if (rec) {
+        rec->fRadius = SkBlurMask::ConvertSigmaToRadius(fSigma);
+        rec->fColor = fBlurColor;
+        rec->fOffset.set(fDx, fDy);
+    }
+    return true;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////
+
 SkDrawLooper::Context* SkBlurDrawLooper::createContext(SkCanvas*, void* storage) const {
     return SkNEW_PLACEMENT_ARGS(storage, BlurDrawLooperContext, (this));
 }