Fix a pref test -- Win/Linux don't have browser.show_page_options_buttons pref

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 a2b7166d51f5eaefb9377861d7ab6fd464365841..2a685cea53c0a2b373a2e260fdadcbb04b4d45ff 100644
--- a/chrome/test/pyautolib/pyauto.py
+++ b/chrome/test/pyautolib/pyauto.py
@@ -179,6 +179,26 @@ class PyUITest(pyautolib.PyUITestBase, unittest.TestCase):
       quoted_path = urllib.quote(abs_path)
       return 'file://' + quoted_path
 
+  @staticmethod
+  def IsMac():
+    """Are we on Mac?"""
+    return 'darwin' == sys.platform
+
+  @staticmethod
+  def IsLinux():
+    """Are we on Linux?"""
+    return 'linux2' == sys.platform
+
+  @staticmethod
+  def IsWin():
+    """Are we on Win?"""
+    return 'win32' == sys.platform
+
+  @staticmethod
+  def IsPosix():
+    """Are we on Mac/Linux?"""
+    return PyUITest.IsMac() or PyUITest.IsLinux()
+
   def WaitUntil(self, function, timeout=-1, retry_sleep=0.25, args=[]):
     """Poll on a condition until timeout.