[Telemetry] Don't create a new Tab object at each navigation.

tools/telemetry/telemetry/core/tab.py

Index: tools/telemetry/telemetry/core/tab.py
diff --git a/tools/telemetry/telemetry/core/tab.py b/tools/telemetry/telemetry/core/tab.py
index 8b677df19c5e58e8b69561ea4d01c2b88fb85e80..2ae7c9f74359464d9b6dd33dad1a443b503b1a61 100644
--- a/tools/telemetry/telemetry/core/tab.py
+++ b/tools/telemetry/telemetry/core/tab.py
@@ -27,9 +27,6 @@ class Tab(web_contents.WebContents):
     super(Tab, self).__init__(inspector_backend)
     self._previous_tab_contents_bounding_box = None
 
-  def __del__(self):
-    super(Tab, self).__del__()
-
   @property
   def browser(self):
     """The browser in which this tab resides."""
@@ -57,7 +54,6 @@ class Tab(web_contents.WebContents):
                                              'event_listener_count']]))
     return dom_counters
 
-
   def Activate(self):
     """Brings this tab to the foreground asynchronously.