Allow controlling the Instant field trial through a command line flag.

chrome/test/functional/instant.py

Index: chrome/test/functional/instant.py
diff --git a/chrome/test/functional/instant.py b/chrome/test/functional/instant.py
index 796b68754389f4ef6b1e24ff8c5d9fcb58f330e8..917b10ff2321a01b58c4f6d37b990f336f6d84b0 100644
--- a/chrome/test/functional/instant.py
+++ b/chrome/test/functional/instant.py
@@ -21,7 +21,6 @@ class InstantSettingsTest(pyauto.PyUITest):
                      msg='Instant is enabled by default.')
     # Enable instant.
     self.SetPrefs(pyauto.kInstantEnabled, True)
-    self.SetPrefs(pyauto.kInstantEnabledOnce, True)
     self.assertTrue(self.GetPrefsInfo().Prefs(pyauto.kInstantEnabled),
                     msg='Instant is not enabled.')
     self.SetOmniboxText('google.com')
@@ -42,7 +41,6 @@ class InstantTest(pyauto.PyUITest):
   def setUp(self):
     pyauto.PyUITest.setUp(self)
     self.SetPrefs(pyauto.kInstantEnabled, True)
-    self.SetPrefs(pyauto.kInstantEnabledOnce, True)
 
   def _DoneLoading(self):
     info = self.GetInstantInfo()