Add pref browser.display.show_loading_image_placeholder from http://hg.mozilla.org/mozilla-central/rev/acc0b3f3daba
Add pref browser.display.show_loading_image_placeholder from http://hg.mozilla.org/mozilla-central/rev/acc0b3f3daba

nth10sd/funfuzz,MozillaSecurity/funfuzz,MozillaSecurity/funfuzz,nth10sd/funfuzz,MozillaSecurity/funfuzz,nth10sd/funfuzz