Add google-sparehash include paths.
Disable critical image beaconing in system tests. With this enabled image inline tests don't work, since only critical images will be inlined.
Add Timer to constructor of NgxRequestContext.
Revert "Add Timer to constructor of NgxRequestContext."

This reverts commit dedd681399210160245802d3886eb36a9b7ec764.
system-test: critical css
Revert "Revert "Add Timer to constructor of NgxRequestContext.""

This reverts commit e80428314245bd667570130c3ce5dacdd8410249.
Add lazyload images with beacon test.
Revert "Add lazyload images with beacon test."

This reverts commit d5ea62cdfcb4b9a438f358436c6d034e2d9b6e4f.