[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

base/strings/string_util.h

Index: base/strings/string_util.h
diff --git a/base/strings/string_util.h b/base/strings/string_util.h
index 5ab2ad5d5477f2a648aa081dda0ad2a5e859754d..3d9ac83da1ab1562515942f153bc8f2d3d063efe 100644
--- a/base/strings/string_util.h
+++ b/base/strings/string_util.h
@@ -500,6 +500,12 @@ BASE_EXPORT bool MatchPattern(const base::StringPiece& string,
 BASE_EXPORT bool MatchPattern(const base::string16& string,
                               const base::string16& pattern);
 
+// Returns offset to the beginning of first occurence of |search| in the |str|.
+// If no such subsequence is found, |base::string16::npos| is returned.
+BASE_EXPORT base::string16::size_type StartsAt(const base::string16& str,
+                                               const base::string16& search,
+                                               bool case_sensitive);
+
 // Hack to convert any char-like type to its unsigned counterpart.
 // For example, it will convert char, signed char and unsigned char to unsigned
 // char.