Bug 881139 - hdpi/xhdpi resolution assets and layout for Clock app

[ian-liu]

• To test this patch on HVGA / WVGA devices:

1. $ make install-gaia APP=fm GAIA_DEV_PIXELS_PER_PX=1.5

What GAIA_DEV_PIXELS_PER_PX do is to replace image files by @1.5x assets when exist.
Images will be too large (and break the layout) if we missed to set background-size for them in the patch.
If this patch works well, we will get correct layout on both HVGA and WVGA (and ideally qHD, but AFAIK we don't have to confirm it at this time) screen.

• Testing on nightly is also possible:

1. $ make DEBUG=1 GAIA_DEV_PIXELS_PER_PX=1.5
2. enter about:config and set layout.css.devPixelsPerPx to 1.5
3. set responsive design window to 320 x 533 px (which is CSS pixel dimension for 480 x 800 device pixel dimension).

But, of course, for apps using specific APIs, not all features can be tested.

[rexboy7]

This line was for responsive.css which is no longer needed, we can remove it.

[ian-liu]

Nice catch! It should be removed.

[rexboy7]

Just curious, does these png files from L68-L87 no longer being used?
https://github.com/ian-liu/gaia/blob/7c6715623b162a2f6a13699a6d8bca653f2acfe4/apps/clock/style/clock.css#L68

[ian-liu]

Yes, these png files from L68-L87 won't be used again. There is no any Dom element for reference these file. They are all old clock app's document which was removed for a long time. :) I have just removed these CSS sheet too. Thanks for your reminder again.

[ian-liu]

Got r+ and revised useless comment. We can merge the pr now. Thanks for @rexboy7 's reviewing effort. It needs more patient for patch.