Tidy up some more integral types.

For #65.

Change-Id: I6794aa075bb81fbb6b6f2bd9076d42daa9b54187
Reviewed-on: https://code-review.googlesource.com/3840
Reviewed-by: Paul Wankadia <[email protected]>
diff --git a/re2/stringpiece.h b/re2/stringpiece.h
index bc8bf40..1479d1a 100644
--- a/re2/stringpiece.h
+++ b/re2/stringpiece.h
@@ -137,17 +137,17 @@
   int max_size() const { return length_; }
   int capacity() const { return length_; }
 
-  int copy(char* buf, size_type n, size_type pos = 0) const;
+  size_type copy(char* buf, size_type n, size_type pos = 0) const;
 
   bool contains(StringPiece s) const;
 
-  int find(const StringPiece& s, size_type pos = 0) const;
-  int find(char c, size_type pos = 0) const;
-  int rfind(const StringPiece& s, size_type pos = npos) const;
-  int rfind(char c, size_type pos = npos) const;
+  size_type find(const StringPiece& s, size_type pos = 0) const;
+  size_type find(char c, size_type pos = 0) const;
+  size_type rfind(const StringPiece& s, size_type pos = npos) const;
+  size_type rfind(char c, size_type pos = npos) const;
 
   StringPiece substr(size_type pos, size_type n = npos) const;
-  
+
   static bool _equal(const StringPiece&, const StringPiece&);
 };