Add tab support to RenderBlockLineLayout::stripTrailingSpace

Add tab support to RenderBlockLineLayout::stripTrailingSpace

Change RenderBlockLineLayout::stripTrailingSpace to measure the width of
the first trailing white-space character instead of always assuming it's
a space character. This fixes a bug where we wrap text unnecessarily for
elements with a trailing tab character as we correctly measure the right
character (tab) when computing the preferred with but subtract the width
of a space character in stripTrailingSpace.

R=pdr@chromium.org
BUG=444544
TEST=fast/text/trailing_whitespace_wrapping.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=187878

[eae, 2015-01-06 00:14:37]

eae@chromium.org changed reviewers:
+ pdr@chromium.org

[pdr., 2015-01-06 00:24:30]

LGTM.

Discussed this offline a bit. Lots of room for improvement in this code
(collapsing into the last whitespace char instead of the last, resizing the
string before we even get here, etc) but because the common case is unaffected,
lets go ahead with this approach.

[pdr., 2015-01-06 00:24:32]

The CQ bit was checked by pdr@chromium.org

[commit-bot: I haz the power, 2015-01-06 00:25:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/836863002/1

[commit-bot: I haz the power, 2015-01-06 01:19:50]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=187878

[falken, 2015-01-06 06:52:08]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/836103002/ by falken@chromium.org.

The reason for reverting is: trailing_whitespace_wrapping.html is crashing on
Mac10.6 (dbg)

http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=fas...

Example:
22:23:47.008 3912 worker/4 fast/text/trailing_whitespace_wrapping.html crashed,
(stderr lines):
22:23:47.008 3912   Assertion failed: (bool (status_and &
kCTRunStatusRightToLeft) == backward), function _hb_coretext_shape, file
../../third_party/harfbuzz-ng/src/hb-coretext.cc, line 989.
22:23:47.009 3881 [30380/38782] fast/text/trailing_whitespace_wrapping.html
failed unexpectedly (renderer crashed [pid=6953]).