Calculate and show the shadow from a spot light.

Change-Id: Ia558852e8cde5d33866b22875eb501e4c6858819
diff --git a/libs/hwui/ShadowTessellator.h b/libs/hwui/ShadowTessellator.h
index 05cb00c..fff00b1 100644
--- a/libs/hwui/ShadowTessellator.h
+++ b/libs/hwui/ShadowTessellator.h
@@ -29,6 +29,14 @@
     static void tessellateAmbientShadow(float width, float height,
             const mat4& casterTransform, VertexBuffer& shadowVertexBuffer);
 
+    static void tessellateSpotShadow(float width, float height,
+            int screenWidth, int screenHeight,
+            const mat4& casterTransform, VertexBuffer& shadowVertexBuffer);
+
+private:
+    static void generateCasterPolygon(float width, float height,
+            const mat4& casterTransform, int vertexCount, Vector3* polygon);
+
 }; // ShadowTessellator
 
 }; // namespace uirenderer