tools/android/loading: Properly detect page loading failures

tools/android/loading/tracing.py

Index: tools/android/loading/tracing.py
diff --git a/tools/android/loading/tracing.py b/tools/android/loading/tracing.py
index 3bf5246fc7e865f0a2cfd0d036e98176756d352d..060136bf09260fa3dadac8fe093d21a61a151eb2 100644
--- a/tools/android/loading/tracing.py
+++ b/tools/android/loading/tracing.py
@@ -86,6 +86,13 @@ class TracingTrack(devtools_monitor.Track):
     return [e for e in matching_events
         if 'frame' in e.args and e.args['frame'] == self.GetMainFrameID()]
 
+  def GetMainFrameRoutingID(self):
+    """Returns the main frame routing ID."""
+    for event in self.GetMatchingEvents(
+        'navigation', 'RenderFrameImpl::OnNavigate'):
+      return event.args['id']
+    assert False
+
   def GetMainFrameID(self):
     """Returns the main frame ID."""
     if not self._main_frame_id: