trunk-tracking: port tests for r3935 which changes image lazyloading
trunk-tracking: port tests for r3937, url-valued attributes overriding spec
trunk-tracking: port r3945 which made the location of static assets configurable
trunk-tracking: port tests for r3948, PageSpeed=... not ModPagespeed=...
trunk-tracking: fix comment
Merge pull request #675 from pagespeed/jefftk-update-trunk-tracking

trunk tracking: update from r3934 to r3949