Warnings about ferrum

[route]

@Mifrill I think we can remove it, agree

[Mifrill]

@jamarat thanks for the raising the flag!

The first case looks weird:

https://github.com/Mifrill/ferrum/blob/master/lib/ferrum/context.rb#L44-L52

    def create_target
      target_id = @browser.command("Target.createTarget",
                                   browserContextId: @id,
                                   url: "about:blank")["targetId"]
      target = @pendings.take(@browser.timeout)
      raise NoSuchTargetError unless target.is_a?(Target)
      @targets[target.id] = target
      target
    end

we probably should remove the declaration of target_id at all here:

	  target = @pendings.take(@browser.timeout)
      raise NoSuchTargetError unless target.is_a?(Target)
      @targets[target.id] = target
      target

or we should to apply something like this:

target = @targets[target_id] || @pendings.take(@browser.timeout)

because we may have nothing in @pendings Concurrent::MVar on @pendings.take fire, according to logic in #add_target:

	def add_target(params)
      target = Target.new(@browser, params)
      if target.window?
        @targets[target.id] = target
      else
        @pendings.put(target, @browser.timeout)
      end
    end

[Mifrill]

@route we can't just remove this declaration, because we should trigger the subscriber event here:
https://github.com/Mifrill/ferrum/blob/ecab9ec5a0aa8454e7021bc5fcfc8c5f1c3fb6f7/lib/ferrum/contexts.rb#L48
by browser.client.on("Target.targetCreated") to Creates a new page.
https://chromedevtools.github.io/devtools-protocol/tot/Target/#method-createTarget