Add the ability to run a callback between fork and exec.

base/process/process_unittest.cc

Index: base/process/process_unittest.cc
diff --git a/base/process/process_unittest.cc b/base/process/process_unittest.cc
index 5180f64c55a8111a5db6456570d1ac4d38f2776e..14a934c123511c09056be6ee9614ed06d5dcf4ae 100644
--- a/base/process/process_unittest.cc
+++ b/base/process/process_unittest.cc
@@ -4,6 +4,8 @@
 
 #include "base/process/process.h"
 
+#include "base/bind.h"
+#include "base/posix/eintr_wrapper.h"
 #include "base/process/kill.h"
 #include "base/test/multiprocess_test.h"
 #include "base/test/test_timeouts.h"
@@ -201,4 +203,40 @@ TEST_F(ProcessTest, SetProcessBackgroundedSelf) {
   EXPECT_EQ(old_priority, new_priority);
 }
 
+#if defined(OS_POSIX)
+const char kPipeValue = '\xcc';
+
+void ReadFromPipe(int fd) {
+  char c;
+  RAW_CHECK(HANDLE_EINTR(read(fd, &c, 1)) == 1);
+  RAW_CHECK(IGNORE_EINTR(close(fd)) == 0);
+  RAW_CHECK(c == kPipeValue);
+}
+
+TEST_F(ProcessTest, PreExecHook) {
+  int pipe_fds[2];
+  ASSERT_EQ(0, pipe(pipe_fds));
+
+  int read_fd = pipe_fds[0];
+  int write_fd = pipe_fds[1];
+  base::FileHandleMappingVector fds_to_remap;
+  fds_to_remap.push_back(std::make_pair(read_fd, read_fd));
+
+  LaunchOptions options;
+  options.fds_to_remap = &fds_to_remap;
+  options.pre_exec_hook = base::Bind(&ReadFromPipe, read_fd);
+  Process process(SpawnChildWithOptions("SimpleChildProcess", options));
+  ASSERT_TRUE(process.IsValid());
+
+  ASSERT_EQ(0, IGNORE_EINTR(close(read_fd)));
+  ASSERT_EQ(1, HANDLE_EINTR(write(write_fd, &kPipeValue, 1)));
+  ASSERT_EQ(0, IGNORE_EINTR(close(write_fd)));
+
+  const int kDummyExitCode = 42;
+  int exit_code = kDummyExitCode;

[jln (very slow on Chromium), 2015/01/06 00:43:36]

= 42?

+  EXPECT_TRUE(process.WaitForExit(&exit_code));
+  EXPECT_EQ(0, exit_code);
+}
+#endif
+
 }  // namespace base