Fix positioning of 1 pixel wide lines (esp. non AA lines.)

Change-Id: Ic155cac72f351edae35dffdfbb236954f57ba7de
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index eb85169..02b1425 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -633,7 +633,7 @@
             mLine.update(points[i], points[i + 1], points[i + 2], points[i + 3],
                     strokeWidth, tx, ty);
         } else {
-            ty = -strokeWidth * 0.5f;
+            ty = strokeWidth <= 1.0f ? 0.0f : -strokeWidth * 0.5f;
         }
 
         const float dx = points[i + 2] - points[i];