Remove implicit uint8_t to char cast in string replace.

R=jkummerow@chromium.org
BUG=446196
LOG=Y

Review URL: https://codereview.chromium.org/864753003

Cr-Commit-Position: refs/heads/master@{#26181}

src/runtime/runtime-regexp.cc

@@ -278,7 +278,7 @@ void CompiledReplacement::Apply(ReplacementStringBuilder* builder,
 }
 
 
-void FindOneByteStringIndices(Vector<const uint8_t> subject, char pattern,
+void FindOneByteStringIndices(Vector<const uint8_t> subject, uint8_t pattern,
                               ZoneList<int>* indices, unsigned int limit,
                               Zone* zone) {
   DCHECK(limit > 0);