Revert the revert in https://codereview.chromium.org/323713002/ and fix the bug.

tools/telemetry/telemetry/core/backends/chrome/inspector_backend.py

Index: tools/telemetry/telemetry/core/backends/chrome/inspector_backend.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/inspector_backend.py b/tools/telemetry/telemetry/core/backends/chrome/inspector_backend.py
index 3d1e81bcc92bdf886235ace15ce6a3b6ea659787..b70c15bc27677099d029ab723081d69793c87127 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/inspector_backend.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/inspector_backend.py
@@ -74,16 +74,12 @@ class InspectorBackend(inspector_websocket.InspectorWebsocket):
   @property
   def url(self):
     for c in self._browser_backend.ListInspectableContexts():
-      if c['id'] == self.id:
+      if c['id'] == self._context['id']:
         return c['url']
     return None
 
   @property
   def id(self):
-    return self._context['id']
-
-  @property
-  def id(self):
     return self.debugger_url
 
   @property
@@ -220,7 +216,7 @@ class InspectorBackend(inspector_websocket.InspectorWebsocket):
 
   def _IsInspectable(self):
     contexts = self._browser_backend.ListInspectableContexts()
-    return self.id in [c['id'] for c in contexts]
+    return self._context['id'] in [c['id'] for c in contexts]
 
   def _HandleNotification(self, res):
     if (res['method'] == 'Inspector.detached' and