Threads can race to be the first one to calculate the empty path ref's bounds.

include/core/SkPathRef.h

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPathRef_DEFINED
 #define SkPathRef_DEFINED
@@ skipping 94 matching lines @@
     };
 
 public:
     /**
      * Gets a path ref with no verbs or points.
      */
     static SkPathRef* CreateEmpty() {
         static SkPathRef* gEmptyPathRef;
         if (!gEmptyPathRef) {
             gEmptyPathRef = SkNEW(SkPathRef); // leak!
+            gEmptyPathRef->computeBounds();   // Premptively avoid a race to clear fBoundsIsDirty.
         }
         return SkRef(gEmptyPathRef);
     }
 
     /**
      *  Returns true if all of the points in this path are finite, meaning there
      *  are no infinities and no NaNs.
      */
     bool isFinite() const {
         if (fBoundsIsDirty) {
@@ skipping 231 matching lines @@
     enum {
         kEmptyGenID = 1, // GenID reserved for path ref with zero points and zero verbs.
     };
     mutable int32_t     fGenerationID;
     SkDEBUGCODE(int32_t fEditorsAttached;) // assert that only one editor in use at any time.
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif