Rename tab_backend to inspector_backend.

tools/telemetry/telemetry/inspector_runtime.py

Index: tools/telemetry/telemetry/inspector_runtime.py
===================================================================
--- tools/telemetry/telemetry/inspector_runtime.py	(revision 179778)
+++ tools/telemetry/telemetry/inspector_runtime.py	(working copy)
@@ -5,9 +5,9 @@
   pass
 
 class InspectorRuntime(object):
-  def __init__(self, tab_backend):
-    self._tab_backend = tab_backend
-    self._tab_backend.RegisterDomain(
+  def __init__(self, inspector_backend):
+    self._inspector_backend = inspector_backend
+    self._inspector_backend.RegisterDomain(
         'Runtime',
         self._OnNotification,
         self._OnClose)
@@ -44,7 +44,7 @@
         'returnByValue': True
         }
       }
-    res = self._tab_backend.SyncRequest(request, timeout)
+    res = self._inspector_backend.SyncRequest(request, timeout)
     if 'error' in res:
       raise EvaluateException(res['error']['message'])