How can i get fully loaded html through python-mechanize?

Question

Hi I'm using python mechanize to get datas from webpages. I'm trying to get imgurl from google image search webpage to download search result images.

Here's my code I fill search form as 'dog' and submit. (search 'dog')

import mechanize
import cookielib
import urllib2
import urllib

br = mechanize.Browser()
cj = cookielib.LWPCookieJar()
br.set_cookiejar(cj)
br.set_handle_equiv(True)
br.set_handle_redirect(True)
br.set_handle_robots(False)
br.set_handle_refresh(mechanize._http.HTTPRefreshProcessor(), max_time = 1)
br.addheaders = [('User-agent', 'Mozilla/5.0 (x11; U; Linux i686; en-US; rv:1.9.0.1) Gecko/2008071615 Fedora/3.0.1-1.fc9 Firefox/3.0.1'), ('Accept', '*/*') ,('Accept-Language', 'ko-KR')]

br.open('http://www.google.com/imghp?hl=en')
br.select_form(nr=0)
br.form['q'] = 'dog'
a = br.submit()
searched_url = br.geturl()

file0 = open("1.html", "wb")
file0.write(a.read())
file0.close()

when i see page-source from chrome browser, there are 'imgurl's in pagesource. But when i read data from python mechanize, there's no such things. also, the size of 1.html(which i write by python) is much smaller than html file downloaded from chrome. How can i get exactly same html data as web-browsers by using python?

Do i have to set request headers same as web-browsers? thanks