Add initial hidden outline APIs

Background drawable outline usage and drawable outline calculation
still to come.

Change-Id: I8c7539f1638f86e1f8eb11f4fe49f705f61d58ba
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index 7a11948..b710825 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -3199,6 +3199,11 @@
     PathTessellator::approximatePathOutlineVertices(*casterOutline,
             casterRefinementThresholdSquared, casterVertices2d);
 
+    if (casterVertices2d.size() == 0) {
+        // empty caster polygon computed from path
+        return DrawGlInfo::kStatusDone;
+    }
+
     // map 2d caster poly into 3d
     const int casterVertexCount = casterVertices2d.size();
     Vector3 casterPolygon[casterVertexCount];