Move handleFrameTree

handleFrameTree is called when a new frame session is created for a new
frame that is attached. Some of these frames are not mainframes but do
contains a tree structures with child frames. If we don't handle the
frame tree for these non-mainframes, this will prevent navigations from
being handled for these frames and a panic/error which would stop the
test iteration.

common/frame_session.go

@@ -406,8 +406,9 @@ func (fs *FrameSession) initFrameTree() error {
  return fmt.Errorf("got a nil page frame tree")
  }
 
+ fs.handleFrameTree(frameTree)
+
  if fs.isMainFrame() {
- fs.handleFrameTree(frameTree)
  fs.initRendererEvents()
  }
  return nil