Added a timezone policy and pyauto tests for it.

chrome/test/pyautolib/pyauto.py

Index: chrome/test/pyautolib/pyauto.py
diff --git a/chrome/test/pyautolib/pyauto.py b/chrome/test/pyautolib/pyauto.py
index dfe25d69bf43b129f724881405d67290df00a2aa..2b557add04f519161622de3d4f91896f719c988a 100755
--- a/chrome/test/pyautolib/pyauto.py
+++ b/chrome/test/pyautolib/pyauto.py
@@ -5406,11 +5406,12 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
     """Sets the timezone on ChromeOS. A user must be logged in.
 
     The timezone is the relative path to the timezone file in
-    /usr/share/zoneinfo. For example, /usr/share/zoneinfo/America/Los_Angeles
-    is 'America/Los_Angeles'.
+    /usr/share/zoneinfo. For example, /usr/share/zoneinfo/America/Los_Angeles is
+    'America/Los_Angeles'. For a list of valid timezones see
+    'chrome/browser/chromeos/system/timezone_settings.cc'.
 
     This method does not return indication of success or failure.
-    If the timezone is invalid, it falls back to UTC/GMT.
+    If the timezone is it falls back to a valid timezone.
 
     Raises:
       pyauto_errors.JSONInterfaceError if the automation call returns an error.
@@ -5619,6 +5620,25 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
     cmd_dict = { 'command': 'CaptureProfilePhoto' }
     return self._GetResultFromJSONRequest(cmd_dict)
 
+  def SetCrosSetting(self, path, value):
+    """Set CrosSetting for the given path to the given value.
+
+    CrosSettings are not handled by PrefService but by the class
+    chromeos::CrosSettings. Therefore, we need this separate function besides
+    SetPrefs.
+
+    Args:
+      path: the path the preference key that needs to be changed
+            example: "cros.system.timezone"
+      value: the value to be set.
+    """
+    cmd_dict = {
+      'command': 'SetCrosSetting',
+      'path': path,
+      'value': value,
+    }
+    self._GetResultFromJSONRequest(cmd_dict, windex=None)
+
   def GetMemoryStatsChromeOS(self, duration):
     """Identifies and returns different kinds of current memory usage stats.