Revert of Remove some legacy versions of StartsWith and EndsWith.

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 755215c0850da117aa664fbc67a10285d3054456..d7a08c869bcba0e18b4c842f1a454d3ff4c9f6f4 100644
--- a/base/strings/string_util.h
+++ b/base/strings/string_util.h
@@ -381,6 +381,19 @@
                     case_sensitive ? CompareCase::SENSITIVE
                                    : CompareCase::INSENSITIVE_ASCII);
 }
+BASE_EXPORT bool StartsWith(const string16& str,
+                            const string16& search,
+                            bool case_sensitive);
+inline bool EndsWith(const std::string& str,
+                     const std::string& search,
+                     bool case_sensitive) {
+  return EndsWith(StringPiece(str), StringPiece(search),
+                  case_sensitive ? CompareCase::SENSITIVE
+                                 : CompareCase::INSENSITIVE_ASCII);
+}
+BASE_EXPORT bool EndsWith(const string16& str,
+                          const string16& search,
+                          bool case_sensitive);
 
 // Determines the type of ASCII character, independent of locale (the C
 // library versions will change based on locale).