Leave it up to the driver to make sure that resetting is synchronous

I think that this was a futile attempt to resolve problems with restting sessions which should be much better handled by the addition of `wait_for_pending_requests`.

Closes #1670

lib/capybara/driver/base.rb

@@ -134,8 +134,4 @@ class Capybara::Driver::Base
   def needs_server?
     false
   end
-
-  def browser_initialized?
-    true
-  end
 end

lib/capybara/rack_test/driver.rb

@@ -87,10 +87,6 @@ class Capybara::RackTest::Driver < Capybara::Driver::Base
     @browser = nil
   end
 
-  def browser_initialized?
-    !@browser.nil?
-  end
-
   def get(*args, &block); browser.get(*args, &block); end
   def post(*args, &block); browser.post(*args, &block); end
   def put(*args, &block); browser.put(*args, &block); end

lib/capybara/selenium/driver.rb

@@ -248,10 +248,6 @@ class Capybara::Selenium::Driver < Capybara::Driver::Base
     Selenium::WebDriver::Error::NoSuchWindowError
   end
 
-  def browser_initialized?
-    !@browser.nil?
-  end
-
   private
 
   def within_given_window(handle)

lib/capybara/session.rb

@@ -107,7 +107,6 @@ module Capybara
     def reset!
       if @touched
         driver.reset!
-        assert_no_selector :xpath, "/html/body/*" if driver.browser_initialized?
         @touched = false
       end
       @server.wait_for_pending_requests if @server