Match spec for font-weight: bolder|lighter

Match spec for font-weight: bolder|lighter

Currently, bolder and lighter change font-weight in a non-compliant way
The spec (http://www.w3.org/TR/css3-fonts/#bolderlighter) defines
exactly what the computed values should be given the inherited weight
values, so we should match those.

The removed FIXME's for selecting the next lightest/heaviest weight from
the used font family seems to refer to behaviour from
CSS1 (http://www.w3.org/TR/CSS1/#font-weight), while this is replaced
with a simpler procedure for resolving bolder and lighter in font weights
in CSS2 (http://www.w3.org/TR/CSS2/fonts.html#propdef-font-weight) and
CSS3 (link above).

BUG=242041
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=153116

[eseidel, 2013-06-06 07:02:26]

lgtm, but ojan or jparent may be better reviewers for this?

You might consider submitting this to webkit.org for a second opinion as well.

[commit-bot: I haz the power, 2013-06-26 06:08:22]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/timloh@chromium.org/15994009/1

[Timothy Loh, 2013-06-26 06:10:21]

Forgot about this change! ksakamoto came up with the exact same change to
FontDescription.cpp since I didn't link this CL to the original bug.

[commit-bot: I haz the power, 2013-06-26 06:20:02]

Retried try job too often on blink_presubmit for step(s) presubmit
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=blink_pres...

[commit-bot: I haz the power, 2013-06-26 06:22:40]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/timloh@chromium.org/15994009/1

[commit-bot: I haz the power, 2013-06-26 06:35:56]

Retried try job too often on blink_presubmit for step(s) presubmit
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=blink_pres...

[commit-bot: I haz the power, 2013-06-26 06:37:50]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/timloh@chromium.org/15994009/15001

[commit-bot: I haz the power, 2013-06-26 06:48:36]

Retried try job too often on blink_presubmit for step(s) presubmit
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=blink_pres...

[commit-bot: I haz the power, 2013-06-27 03:41:49]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/timloh@chromium.org/15994009/15001

[commit-bot: I haz the power, 2013-06-27 04:57:07]

Change committed as 153116