Adds function for activating a tab.

tools/telemetry/telemetry/tab.py

Index: tools/telemetry/telemetry/tab.py
diff --git a/tools/telemetry/telemetry/tab.py b/tools/telemetry/telemetry/tab.py
index 7f3730fa8e8b246947126299582b2d5ca7a986a6..43a509a4a282975a3cc5620774addb8c711c999d 100644
--- a/tools/telemetry/telemetry/tab.py
+++ b/tools/telemetry/telemetry/tab.py
@@ -1,6 +1,7 @@
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
+
 from telemetry import inspector_backend
 from telemetry import inspector_console
 from telemetry import inspector_page
@@ -68,6 +69,10 @@ class Tab(object):
     self.Disconnect()
     self._tab_controller.CloseTab(self._debugger_url)
 
+  def Activate(self):
+    """Brings this tab to the foreground."""
+    self._tab_controller.ActivateTab(self._debugger_url)
+
   @property
   def browser(self):
     """The browser in which this tab resides."""