Add Socket::ReadIfReady()

net/socket/tcp_client_socket.h

Index: net/socket/tcp_client_socket.h
diff --git a/net/socket/tcp_client_socket.h b/net/socket/tcp_client_socket.h
index 65a51837103e87c272639820f5a23aca0bac1e7a..8981fb066f55c18dcae07fd2bcfef28668ef77b7 100644
--- a/net/socket/tcp_client_socket.h
+++ b/net/socket/tcp_client_socket.h
@@ -68,6 +68,9 @@ class NET_EXPORT TCPClientSocket : public StreamSocket {
   int Read(IOBuffer* buf,
            int buf_len,
            const CompletionCallback& callback) override;
+  int ReadIfReady(IOBuffer* buf,
+                  int buf_len,
+                  const CompletionCallback& callback) override;
   int Write(IOBuffer* buf,
             int buf_len,
             const CompletionCallback& callback) override;
@@ -90,6 +93,13 @@ class NET_EXPORT TCPClientSocket : public StreamSocket {
     CONNECT_STATE_NONE,
   };
 
+  // A helper method shared by Read() and ReadIfReady(). If |read_if_ready| is
+  // set to true, ReadIfReady() will be used instead of Read().
+  int ReadCommon(IOBuffer* buf,
+                 int buf_len,
+                 const CompletionCallback& callback,
+                 bool read_if_ready);
+
   // State machine used by Connect().
   int DoConnectLoop(int result);
   int DoConnect();