Add alternative ambient shadow method to Android shadow sample

include/effects/SkGaussianEdgeShader.h

Index: include/effects/SkGaussianEdgeShader.h
diff --git a/include/effects/SkGaussianEdgeShader.h b/include/effects/SkGaussianEdgeShader.h
new file mode 100644
index 0000000000000000000000000000000000000000..97472a238b498ba13f950a6864ece16d96bfe264
--- /dev/null
+++ b/include/effects/SkGaussianEdgeShader.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkGaussianEdgeShader_DEFINED
+#define SkGaussianEdgeShader_DEFINED
+
+#include "SkShader.h"
+
+class SK_API SkGaussianEdgeShader {
+public:
+    /** Returns a shader that applies a Gaussian blur depending on distance to the edge

[robertphillips, 2016/08/16 17:56:07]

* Currently this is only useable by XXX with the GPU backend ?

[jvanverth1, 2016/08/16 19:14:11]

Done.

+    */
+    static sk_sp<SkShader> Make();
+
+    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
+};
+
+#endif