Tessellate on worker threads

Tessellate and cache (where possible) shadow and round rect
tessellation tasks.

Change-Id: I2cfda8e11d83d51ea74af871235cf26e8f831d40
diff --git a/libs/hwui/SpotShadow.h b/libs/hwui/SpotShadow.h
index fb3e6d5..d65ea89 100644
--- a/libs/hwui/SpotShadow.h
+++ b/libs/hwui/SpotShadow.h
@@ -26,7 +26,7 @@
 
 class SpotShadow {
 public:
-    static VertexBufferMode createSpotShadow(bool isCasterOpaque, const Vector3* poly,
+    static void createSpotShadow(bool isCasterOpaque, const Vector3* poly,
             int polyLength, const Vector3& lightCenter, float lightSize,
             int lightVertexCount, VertexBuffer& retStrips);