Enforce SafetyMode for YouTube if prefs::kForceSafeSearch is on.

base/strings/string_util.cc

Index: base/strings/string_util.cc
diff --git a/base/strings/string_util.cc b/base/strings/string_util.cc
index e64b95f7635dc1ddeec4d8f0d97b4d92c0d9b2e3..4840699cf0455525a4ba9e1d607878180cd38aae 100644
--- a/base/strings/string_util.cc
+++ b/base/strings/string_util.cc
@@ -617,6 +617,30 @@ string16 JoinString(const std::vector<string16>& parts,
   return JoinStringT(parts, separator);
 }
 
+static std::string JoinStringKeyValuePair(
+    const StringPairs::value_type& key_value,
+    char delimiter) {
+  return key_value.first + delimiter + key_value.second;
+}
+
+std::string JoinStringKeyValuePairs(const StringPairs& pairs,
+                                    char key_value_delimiter,
+                                    char key_value_pair_delimiter) {
+  if (pairs.empty())
+    return std::string();
+
+  StringPairs::const_iterator it = pairs.begin();
+  std::string result = JoinStringKeyValuePair(*it, key_value_delimiter);
+  ++it;
+
+  for (; it != pairs.end(); ++it) {
+    result += key_value_pair_delimiter;
+    result += JoinStringKeyValuePair(*it, key_value_delimiter);
+  }
+
+  return result;
+}
+
 template<class FormatStringType, class OutStringType>
 OutStringType DoReplaceStringPlaceholders(const FormatStringType& format_string,
     const std::vector<OutStringType>& subst, std::vector<size_t>* offsets) {