Rename tab_backend to inspector_backend.

tools/telemetry/telemetry/tab_list_backend.py

Index: tools/telemetry/telemetry/tab_list_backend.py
===================================================================
--- tools/telemetry/telemetry/tab_list_backend.py	(revision 179778)
+++ tools/telemetry/telemetry/tab_list_backend.py	(working copy)
@@ -9,7 +9,7 @@
 
 from telemetry import browser_gone_exception
 from telemetry import tab
-from telemetry import tab_backend
+from telemetry import inspector_backend
 from telemetry import util
 
 class BrowserConnectionGoneException(
@@ -102,9 +102,10 @@
     # Lazily get/create a Tab object.
     tab_object = self._tab_dict.get(debugger_url)
     if not tab_object:
-      backend = tab_backend.TabBackend(self._browser_backend.browser,
-                                       self._browser_backend,
-                                       debugger_url)
+      backend = inspector_backend.InspectorBackend(
+          self._browser_backend.browser,
+          self._browser_backend,
+          debugger_url)
       tab_object = tab.Tab(backend)
       self._tab_dict[debugger_url] = tab_object
     return tab_object