Fix -INT_MIN integer overflow in itoa_r().

base/debug/stack_trace_posix.cc

Index: base/debug/stack_trace_posix.cc
diff --git a/base/debug/stack_trace_posix.cc b/base/debug/stack_trace_posix.cc
index 2eac14e35380d12dd426add3001de08d910ecc08..9593962d3aa838019b839c3df8a36ff9facd2a83 100644
--- a/base/debug/stack_trace_posix.cc
+++ b/base/debug/stack_trace_posix.cc
@@ -784,7 +784,8 @@ char *itoa_r(intptr_t i, char *buf, size_t sz, int base, size_t padding) {
 
   // Handle negative numbers (only for base 10).
   if (i < 0 && base == 10) {
-    j = -i;
+    // This does "j = -i" while avoiding integer overflow.
+    j = static_cast<uintptr_t>(-(i + 1)) + 1;
 
     // Make sure we can write the '-' character.
     if (++n > sz) {