Replace usage of WebVector::isEmpty with WebVector::empty().

content/child/webmessageportchannel_impl.cc

Index: content/child/webmessageportchannel_impl.cc
diff --git a/content/child/webmessageportchannel_impl.cc b/content/child/webmessageportchannel_impl.cc
index 7ae8468049cb56a8442457ab598cd3913b443b91..bf9b533472d2469845628fae013e4f1a8ad6a221 100644
--- a/content/child/webmessageportchannel_impl.cc
+++ b/content/child/webmessageportchannel_impl.cc
@@ -100,7 +100,7 @@ void WebMessagePortChannelImpl::postMessage(
     const WebString& encoded_message,
     WebMessagePortChannelArray channels) {
   std::vector<MessagePort> ports;
-  if (!channels.isEmpty()) {
+  if (!channels.empty()) {
     ports.resize(channels.size());
     for (size_t i = 0; i < channels.size(); ++i) {
       ports[i] = static_cast<WebMessagePortChannelImpl*>(channels[i].get())->