Quick reject empty paths

bug:7260035

Adding a circle of radius 0 to a path is a no-op in skia, so detect
this case both in the PathRenderer, and in quickReject().

Change-Id: I7a172db49a5d5351b4734b39d4e4ca6379658096
diff --git a/libs/hwui/PathRenderer.cpp b/libs/hwui/PathRenderer.cpp
index 4a66c62..5b55c2b 100644
--- a/libs/hwui/PathRenderer.cpp
+++ b/libs/hwui/PathRenderer.cpp
@@ -323,6 +323,11 @@
     convexPathPerimeterVertices(path, threshInvScaleX * threshInvScaleX,
             threshInvScaleY * threshInvScaleY, tempVertices);
 
+    if (!tempVertices.size()) {
+        // path was empty, return without allocating vertex buffer
+        return;
+    }
+
 #if VERTEX_DEBUG
     for (unsigned int i = 0; i < tempVertices.size(); i++) {
         ALOGD("orig path: point at %f %f", tempVertices[i].position[0], tempVertices[i].position[1]);