Update dynamic_annotations.h to r3494.

base/third_party/dynamic_annotations/dynamic_annotations.h

 /* Copyright (c) 2011, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 530 matching lines @@
   RUNNING_ON_VALGRIND and other valgrind "client requests".
   The file "valgrind.h" may be obtained by doing
      svn co svn://svn.valgrind.org/valgrind/trunk/include
 
   If for some reason you can't use "valgrind.h" or want to fake valgrind,
   there are two ways to make this function return non-zero:
     - Use environment variable: export RUNNING_ON_VALGRIND=1
     - Make your tool intercept the function RunningOnValgrind() and
       change its return value.
  */
-int RunningOnValgrind(void);
+int RunningOnValgrind(void) DYNAMIC_ANNOTATIONS_ATTRIBUTE_WEAK;
 #endif /* DYNAMIC_ANNOTATIONS_PROVIDE_RUNNING_ON_VALGRIND == 1 */
 
 #ifdef __cplusplus
 }
 #endif
 
 #if DYNAMIC_ANNOTATIONS_ENABLED != 0 && defined(__cplusplus)
 
   /* ANNOTATE_UNPROTECTED_READ is the preferred way to annotate racey reads.
 
@@ skipping 24 matching lines @@
       static static_var ## _annotator the ## static_var ## _annotator;\
     }
 #else /* DYNAMIC_ANNOTATIONS_ENABLED == 0 */
 
   #define ANNOTATE_UNPROTECTED_READ(x) (x)
   #define ANNOTATE_BENIGN_RACE_STATIC(static_var, description)  /* empty */
 
 #endif /* DYNAMIC_ANNOTATIONS_ENABLED */
 
 #endif  /* __DYNAMIC_ANNOTATIONS_H__ */