StringToUint should output zero on negative numbers.

base/strings/string_number_conversions.cc

Index: base/strings/string_number_conversions.cc
diff --git a/base/strings/string_number_conversions.cc b/base/strings/string_number_conversions.cc
index 07248501e3156e87ddb4035e81cc73ec5cea749c..f4cf6ec521f1cd0d1c663df54bc792a67a76bc3c 100644
--- a/base/strings/string_number_conversions.cc
+++ b/base/strings/string_number_conversions.cc
@@ -146,6 +146,7 @@ class IteratorRangeToNumber {
 
     if (begin != end && *begin == '-') {
       if (!std::numeric_limits<value_type>::is_signed) {
+        *output = 0;
         valid = false;
       } else if (!Negative::Invoke(begin + 1, end, output)) {
         valid = false;