Use process_singleton_linux on Mac.

base/process/process_handle_mac.cc

Index: base/process/process_handle_mac.cc
diff --git a/base/process/process_handle_mac.cc b/base/process/process_handle_mac.cc
index 6cb8d686e4d77c1a605e6d18b5f0613fb398da90..89d54e663e3fc8aac422d463d224b5f6084a0776 100644
--- a/base/process/process_handle_mac.cc
+++ b/base/process/process_handle_mac.cc
@@ -4,6 +4,7 @@
 
 #include "base/process/process_handle.h"
 
+#include <libproc.h>
 #include <sys/sysctl.h>
 #include <sys/types.h>
 
@@ -24,4 +25,13 @@ ProcessId GetParentProcessId(ProcessHandle process) {
   return info.kp_eproc.e_ppid;

[Scott Hess - ex-Googler, 2014/04/14 19:21:33]

Weird, I wonder why this isn't just getppid()?  The Linux version is also a bit
more convoluted than seems reasonable.

[jackhou1, 2014/04/17 07:55:54]

Yeah, I'm not sure. I'll rope one of the authors of process_singleton_linux to
take a look at this CL later.

[mattm, 2014/04/17 21:44:54]

Heh, I had to stare at it a while too. It's because this allows you to get the
parent pid of an arbitrary process, not just the current one.
It's obvious once you look at how it's used: 
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/pro...

 }
 
+

[Scott Hess - ex-Googler, 2014/04/14 19:21:33]

excess newline.

[jackhou1, 2014/04/17 07:55:54]

Done.

+FilePath GetProcessExecutablePath(ProcessHandle process) {
+  char pathbuf[PROC_PIDPATHINFO_MAXSIZE];

[Scott Hess - ex-Googler, 2014/04/14 19:21:33]

This seems weird - this constant is defined as 4*MAXPATHLEN, and proc_pidpath
defines the buffer as void*.  Is there any chance that this is actually giving
your 32-bit chars?

Looking at libproc.c, it's using strlen() on the buffer, so I guess not.

[jackhou1, 2014/04/17 07:55:54]

Yeah I think 4* MAXPATHLEN just happens to be the upper bound. Looks like the
buffer size needs to be at minimum MAXPATHLEN (PROC_PIDPATHINFO_SIZE).

+  if (!proc_pidpath(process, pathbuf, sizeof(pathbuf)))
+    return FilePath();
+
+  return FilePath(pathbuf);
+}
+
 }  // namespace base