Avoid WTF::Vector::at() and operator[] in core/html.

third_party/WebKit/Source/core/html/forms/EmailInputType.cpp

Index: third_party/WebKit/Source/core/html/forms/EmailInputType.cpp
diff --git a/third_party/WebKit/Source/core/html/forms/EmailInputType.cpp b/third_party/WebKit/Source/core/html/forms/EmailInputType.cpp
index 8891afb63e7081218fa3a9b9f5d8f7df1f5cc55d..755ae39ddb5aa61af50616607431d2c6bdadbf52 100644
--- a/third_party/WebKit/Source/core/html/forms/EmailInputType.cpp
+++ b/third_party/WebKit/Source/core/html/forms/EmailInputType.cpp
@@ -186,8 +186,8 @@ String EmailInputType::findInvalidAddress(const String& value) const {
     return isValidEmailAddress(ensureEmailRegexp(), value) ? String() : value;
   Vector<String> addresses;
   value.split(',', true, addresses);
-  for (unsigned i = 0; i < addresses.size(); ++i) {
-    String stripped = stripLeadingAndTrailingHTMLSpaces(addresses[i]);
+  for (const auto& address : addresses) {
+    String stripped = stripLeadingAndTrailingHTMLSpaces(address);
     if (!isValidEmailAddress(ensureEmailRegexp(), stripped))
       return stripped;
   }