Remove the Mac-specific implementation of LaunchApp, and share the Linux version.

base/process_util.h

Index: base/process_util.h
diff --git a/base/process_util.h b/base/process_util.h
index 31d8de73a3ad24bd596536d8485deae3efe3a0a3..450dbc2893bb08ca24ea7493e830aa05dd3a8132 100644
--- a/base/process_util.h
+++ b/base/process_util.h
@@ -142,7 +142,7 @@ typedef std::vector<std::pair<int, int> > file_handle_mapping_vector;
 bool LaunchApp(const std::vector<std::string>& argv,
                const file_handle_mapping_vector& fds_to_remap,
                bool wait, ProcessHandle* process_handle);
-#if defined(OS_LINUX)
+
 // Similar to above, but also (un)set environment variables in child process
 // through |environ|.
 typedef std::vector<std::pair<const char*, const char*> > environment_vector;
@@ -150,7 +150,6 @@ bool LaunchApp(const std::vector<std::string>& argv,
                const environment_vector& environ,
                const file_handle_mapping_vector& fds_to_remap,
                bool wait, ProcessHandle* process_handle);
-#endif  // defined(OS_LINUX)
 #endif  // defined(OS_POSIX)
 
 // Executes the application specified by cl. This function delegates to one