Temporary instrumentation to help understand lock errors on mac debug bots.

base/synchronization/lock_impl.h

Index: base/synchronization/lock_impl.h
===================================================================
--- base/synchronization/lock_impl.h	(revision 107048)
+++ base/synchronization/lock_impl.h	(working copy)
@@ -17,6 +17,18 @@
 #include "base/base_export.h"
 #include "base/basictypes.h"
 
+#if defined(OS_MACOSX) && !defined(NDEBUG)
+// For Mac debug builds, do some extra checks to make sure a LockImpl is not
+// used after it has been freed. This instrumentation is to help track down
+// spurious locking errors (EINVAL) which are happening on the bots.
+// In particular, I want to make sure they aren't a consequence of having
+// used a freed lock object (which can happen for instance when trying to
+// post tasks to a destroyed MessageLoop).
+// See http://crbug.com/102161 for more details. This instrumentation can be
+// removed once that bug has been identified.
+#define LOCK_IMPL_CHECK_LIVENESS
+#endif
+
 namespace base {
 namespace internal {
 
@@ -53,6 +65,17 @@
 #endif
 
  private:
+#ifdef LOCK_IMPL_CHECK_LIVENESS
+  enum LivenessToken {
+    LT_ALIVE = 0xCa11ab1e,  // 3390155550
+    LT_DELETED = 0xDecea5ed,  // 3738084845
+  };
+
+  void CheckIsAlive();
+
+  LivenessToken liveness_token_;
+#endif  // LOCK_IMPL_CHECK_LIVENESS
+
   OSLockType os_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(LockImpl);