Make sure only the right processes can access the profile path.

chrome/common/chrome_paths.cc

Index: chrome/common/chrome_paths.cc
diff --git a/chrome/common/chrome_paths.cc b/chrome/common/chrome_paths.cc
index 6232b8596984549d6c67dd5fa44d3b02298c6885..513d7bac53ebb17b1bd8a0d066726616a99fed90 100644
--- a/chrome/common/chrome_paths.cc
+++ b/chrome/common/chrome_paths.cc
@@ -14,6 +14,7 @@
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_paths_internal.h"
 #include "chrome/common/chrome_switches.h"
+#include "content/public/common/content_switches.h"
 
 #if defined(OS_MACOSX)
 #include "base/mac/mac_util.h"
@@ -131,6 +132,9 @@ bool PathProvider(int key, FilePath* result) {
   FilePath cur;
   switch (key) {
     case chrome::DIR_USER_DATA:
+      CHECK(ProcessNeedsProfileDir(
+          CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+              switches::kProcessType)));
       if (!GetDefaultUserDataDirectory(&cur)) {
         NOTREACHED();
         return false;