Make the CancellableSyncSocket non-blocking on Send, and blocking on Receive

base/sync_socket_posix.cc

Index: base/sync_socket_posix.cc
diff --git a/base/sync_socket_posix.cc b/base/sync_socket_posix.cc
index c5dca752b2de81da10f475cf30a3e74bc020513c..257916df3357a21962a4f6b9fe7561a09c286d50 100644
--- a/base/sync_socket_posix.cc
+++ b/base/sync_socket_posix.cc
@@ -6,10 +6,11 @@
 
 #include <errno.h>
 #include <limits.h>
+#include <fcntl.h>
 #include <stdio.h>
-#include <sys/types.h>
 #include <sys/ioctl.h>
 #include <sys/socket.h>
+#include <sys/types.h>
 
 #if defined(OS_SOLARIS)
 #include <sys/filio.h>
@@ -95,7 +96,8 @@ size_t SyncSocket::Send(const void* buffer, size_t length) {
   DCHECK_LE(length, kMaxMessageLength);
   const char* charbuffer = static_cast<const char*>(buffer);
   int len = file_util::WriteFileDescriptor(handle_, charbuffer, length);
-  return static_cast<size_t>(len);
+
+  return (len == -1) ? 0 : static_cast<size_t>(len);
 }
 
 size_t SyncSocket::Receive(void* buffer, size_t length) {
@@ -124,6 +126,25 @@ bool CancelableSyncSocket::Shutdown() {
   return HANDLE_EINTR(shutdown(handle(), SHUT_RDWR)) >= 0;
 }
 
+size_t CancelableSyncSocket::Send(const void* buffer, size_t length) {
+  long flags = 0;
+  flags = fcntl(handle_, F_GETFL, NULL);
+  if (flags != -1 && (flags & O_NONBLOCK) == 0) {
+    // Set the socket to non-blocking mode for sending if its original mode
+    // is blocking.
+    fcntl(handle_, F_SETFL, flags | O_NONBLOCK);
+  }
+
+  size_t len = SyncSocket::Send(buffer, length);
+
+  if (flags != -1 && (flags & O_NONBLOCK) == 0) {
+    // Restore the original flags.
+    fcntl(handle_, F_SETFL, flags);
+  }
+
+  return len;
+}
+
 // static
 bool CancelableSyncSocket::CreatePair(CancelableSyncSocket* socket_a,
                                       CancelableSyncSocket* socket_b) {