[chromedriver] Pipe Set Up

Chromedriver will now have the option to connect to Chrome through a
pipe instead of a websocket. In this commit the PipeSetUp method is
added to chrome_lancher to create the two pipes needed to communicate.

Bug: chromedriver:3480
Change-Id: I7e3b70a7ef72b756a092b36d02dc3c091bfeb04f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2336015
Commit-Queue: Lucía Cantú-Miller <cantumiller@google.com>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794652}

chrome/test/chromedriver/chrome_launcher.cc

@@ -65,6 +65,7 @@
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <unistd.h>
 #elif defined(OS_WIN)
 #include "chrome/test/chromedriver/keycode_text_conversion.h"
 #endif
@@ -728,6 +729,33 @@ Status LaunchReplayChrome(network::mojom::URLLoaderFactory* factory,
 
 }  // namespace
 
+Status PipeSetUp(base::LaunchOptions* options, int* write_fd, int* read_fd) {
+#if defined(OS_POSIX)
+
+  int chrome_to_driver_pipe_fds[2];
+  int driver_to_chrome_pipe_fds[2];
+
+  if (pipe(chrome_to_driver_pipe_fds) == -1 ||
+      pipe(driver_to_chrome_pipe_fds) == -1)
+    return Status(kUnknownError, "cannot set up pipe");
+
+  // Numbers 3 & 4 come from kReadDf and kWriteFD in
+  // content/browser/devtools/devtools_pipe_handler.cc
+  options->fds_to_remap.emplace_back(driver_to_chrome_pipe_fds[0], 3);
+  options->fds_to_remap.emplace_back(chrome_to_driver_pipe_fds[1], 4);
+
+  close(driver_to_chrome_pipe_fds[0]);
+  close(chrome_to_driver_pipe_fds[1]);
+
+  *write_fd = driver_to_chrome_pipe_fds[1];
+  *read_fd = chrome_to_driver_pipe_fds[0];
+
+  return Status(kOk);
+#endif
+
+  return Status(kUnknownError, "feature not supported");
+}
+
 Status LaunchChrome(network::mojom::URLLoaderFactory* factory,
                     const SyncWebSocketFactory& socket_factory,
                     DeviceManager* device_manager,