Put app shim IPC socket in a temporary directory. (Mac)

chrome/common/mac/app_mode_common.h

Index: chrome/common/mac/app_mode_common.h
diff --git a/chrome/common/mac/app_mode_common.h b/chrome/common/mac/app_mode_common.h
index a88ded6598f762040990af264ee83f18409c6509..874dd92ca29883758b60f8f5c8e8c058554b8016 100644
--- a/chrome/common/mac/app_mode_common.h
+++ b/chrome/common/mac/app_mode_common.h
@@ -127,6 +127,11 @@ struct ChromeAppModeInfo {
   base::FilePath profile_dir;
 };
 
+// Due to kernel API restraints on the length of the path to a socket, we
+// cannot use a socket under the user data dir. GetShortSocketPath returns a
+// path under /tmp constructed from a hash of the user data dir.
+base::FilePath GetShortSocketPath(const base::FilePath& user_data_dir);
+
 }  // namespace app_mode
 
 #endif  // CHROME_COMMON_MAC_APP_MODE_COMMON_H_