Move all callers of GetHomeDir() to PathService::Get(base::DIR_HOME).

base/file_util_posix.cc

Index: base/file_util_posix.cc
diff --git a/base/file_util_posix.cc b/base/file_util_posix.cc
index 7e7dc052300fde54dc71f36681d783dc14776b17..eef083363c99f697ff525d64afebaf92ac5723c7 100644
--- a/base/file_util_posix.cc
+++ b/base/file_util_posix.cc
@@ -484,8 +484,12 @@ bool GetShmemTempDir(bool executable, FilePath* path) {
 #if !defined(OS_MACOSX)  // Mac implementation is in file_util_mac.mm.
 FilePath GetHomeDir() {
 #if defined(OS_CHROMEOS)
-  if (SysInfo::IsRunningOnChromeOS())
-    return FilePath("/home/chronos/user");
+  if (SysInfo::IsRunningOnChromeOS()) {
+    // On Chrome OS chrome::DIR_USER_DATA is overriden with a primary user
+    // homedir once it becomes available.
+    NOTREACHED() << "Called GetHomeDir() without base::DIR_HOME override";
+    return FilePath("/tmp");

[Dmitry Polukhin, 2014/03/17 18:28:30]

I think it is bad idea to use /tmp attacker could control /tmp. I think we
should use some readonly path. For example even root '/' should be better.

[Will Drewry, 2014/04/08 15:55:04]

'/' is definitely a better choice since it isn't writable.  I'm trying to think
if there's a better alternative, but / is certainly good.  If we had "/empty"
that'd be even better, but it doesn't exist :)

+  }
 #endif
 
   const char* home_dir = getenv("HOME");