Fix loading of data: URI images wrt loadsImagesAutomatically setting

This fixes AwSettingsTest#testBlockNetworkImagesDoesNotBlockDataUrlImage
in Chrome broken after Blink r176642

BUG=356292,387101

Review URL: https://codereview.chromium.org/355043002

git-svn-id: svn://svn.chromium.org/blink/trunk@177425 bbb929c8-8fbe-4397-9dbb-9b2b20218538