Make dynamic_annotations build with -Wconstant-conversion from newer clangs.

base/third_party/dynamic_annotations/dynamic_annotations.c

 /* 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 43 matching lines @@
    The arguments are captured by dynamic tools at runtime. */
 
 #if DYNAMIC_ANNOTATIONS_ENABLED == 1 \
     && DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL == 0
 
 /* Identical code folding(-Wl,--icf=all) countermeasures.
    This makes all Annotate* functions different, which prevents the linker from
    folding them. */
 #ifdef __COUNTER__
 #define DYNAMIC_ANNOTATIONS_IMPL \
-  volatile short lineno = (__LINE__ << 8) + __COUNTER__; (void)lineno;
+  volatile unsigned short lineno = (__LINE__ << 8) + __COUNTER__; (void)lineno;
 #else
 #define DYNAMIC_ANNOTATIONS_IMPL \
-  volatile short lineno = (__LINE__ << 8); (void)lineno;
+  volatile unsigned short lineno = (__LINE__ << 8); (void)lineno;
 #endif
 
 /* WARNING: always add new annotations to the end of the list.
    Otherwise, lineno (see above) numbers for different Annotate* functions may
    conflict. */
 void DYNAMIC_ANNOTATIONS_NAME(AnnotateRWLockCreate)(
     const char *file, int line, const volatile void *lock)
 {DYNAMIC_ANNOTATIONS_IMPL}
 
 void DYNAMIC_ANNOTATIONS_NAME(AnnotateRWLockDestroy)(
@@ skipping 182 matching lines @@
   /* C doesn't have thread-safe initialization of statics, and we
      don't want to depend on pthread_once here, so hack it. */
   int local_running_on_valgrind = running_on_valgrind;
   if (local_running_on_valgrind == -1)
     running_on_valgrind = local_running_on_valgrind = GetRunningOnValgrind();
   return local_running_on_valgrind;
 }
 
 #endif /* DYNAMIC_ANNOTATIONS_PROVIDE_RUNNING_ON_VALGRIND == 1
     && DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL == 0 */