Added a new SafeSPrintf() function that implements snprintf() in an async-safe-fashion

base/debug/stack_trace.h

Index: base/debug/stack_trace.h
diff --git a/base/debug/stack_trace.h b/base/debug/stack_trace.h
index 53bed3c5ac921ed63eaab5eb909db87faedefbcd..00d7c420d3eaf286d71336573437952fcab3152f 100644
--- a/base/debug/stack_trace.h
+++ b/base/debug/stack_trace.h
@@ -77,24 +77,6 @@ class BASE_EXPORT StackTrace {
   size_t count_;
 };
 
-namespace internal {
-
-#if defined(OS_POSIX) && !defined(OS_ANDROID)
-// POSIX doesn't define any async-signal safe function for converting
-// an integer to ASCII. We'll have to define our own version.
-// itoa_r() converts a (signed) integer to ASCII. It returns "buf", if the
-// conversion was successful or NULL otherwise. It never writes more than "sz"
-// bytes. Output will be truncated as needed, and a NUL character is always
-// appended.
-BASE_EXPORT char *itoa_r(intptr_t i,
-                         char *buf,
-                         size_t sz,
-                         int base,
-                         size_t padding);
-#endif  // defined(OS_POSIX) && !defined(OS_ANDROID)
-
-}  // namespace internal
-
 }  // namespace debug
 }  // namespace base