Update from https://crrev.com/333737

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 6f6d6e2b6bd240997c822374adf3126108881d9e..cc7769343b5a592a2d081c89e3203dc82be8f720 100644
--- a/base/strings/string_util.cc
+++ b/base/strings/string_util.cc
@@ -420,14 +420,12 @@ bool IsStringUTF8(const StringPiece& str) {
   return true;
 }
 
-}  // namespace base
-
 template<typename Iter>
 static inline bool DoLowerCaseEqualsASCII(Iter a_begin,
                                           Iter a_end,
                                           const char* b) {
   for (Iter it = a_begin; it != a_end; ++it, ++b) {
-    if (!*b || base::ToLowerASCII(*it) != *b)
+    if (!*b || ToLowerASCII(*it) != *b)
       return false;
   }
   return *b == 0;
@@ -460,18 +458,32 @@ bool LowerCaseEqualsASCII(const char* a_begin,
   return DoLowerCaseEqualsASCII(a_begin, a_end, b);
 }
 
+bool LowerCaseEqualsASCII(const char* a_begin,
+                          const char* a_end,
+                          const char* b_begin,
+                          const char* b_end) {
+  while (a_begin != a_end && b_begin != b_end &&
+         ToLowerASCII(*a_begin) == *b_begin) {
+    a_begin++;
+    b_begin++;
+  }
+  return a_begin == a_end && b_begin == b_end;
+}
+
 bool LowerCaseEqualsASCII(const char16* a_begin,
                           const char16* a_end,
                           const char* b) {
   return DoLowerCaseEqualsASCII(a_begin, a_end, b);
 }
 
-bool EqualsASCII(const string16& a, const base::StringPiece& b) {
+bool EqualsASCII(const string16& a, const StringPiece& b) {
   if (a.length() != b.length())
     return false;
   return std::equal(b.begin(), b.end(), a.begin());
 }
 
+}  // namespace base
+
 bool StartsWithASCII(const std::string& str,
                      const std::string& search,
                      bool case_sensitive) {