Change fallback font collection in HarfBuzzShaper

Change fallback font collection in HarfBuzzShaper

Change HarfBuzzShaper to not populate the fallback font list during text
shaping and instead populate it based on the ShapeResult objects at call
time. This circumvents additional registration work and renders the text
shaping API simpler and more consistent.

R=leviw@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198813

[eae, 2015-07-13 19:55:48]

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

[leviw_travelin_and_unemployed, 2015-07-13 20:47:24]

LGTM

I'm Sheryl I. Guerriero, Gerontologist and I approve this patch.

http://imgur.com/wQs04wY

https://codereview.chromium.org/1239513004/diff/20001/Source/platform/fonts/s...
File Source/platform/fonts/shaping/HarfBuzzShaper.h (right):

https://codereview.chromium.org/1239513004/diff/20001/Source/platform/fonts/s...
Source/platform/fonts/shaping/HarfBuzzShaper.h:74: 
Nit: extra newlines are the devil.

[eae, 2015-07-13 20:50:40]

The CQ bit was checked by eae@chromium.org

[eae, 2015-07-13 20:50:40]

The patchset sent to the CQ was uploaded after l-g-t-m from leviw@chromium.org
Link to the patchset: https://codereview.chromium.org/1239513004/#ps40001
(title: "Kill _ALL_ the new lines")

[commit-bot: I haz the power, 2015-07-13 20:51:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1239513004/40001

[commit-bot: I haz the power, 2015-07-13 23:06:05]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=198813

[eae, 2015-07-14 00:45:17]

A revert of this CL (patchset #3 id:40001) has been created in
https://codereview.chromium.org/1239603002/ by eae@chromium.org.

The reason for reverting is: Caused a number of tests to crash on Mac 10.6
release that previously only crashed on 10.6 debug. 

media/track/track-cue-rendering-rtl.html
inspector/elements/bidi-dom-tree.html
virtual/antialiasedtext/fast/text/trailing_whitespace_wrapping.html
imported/csswg-test/css-writing-modes-3/text-orientation-script-001k.html
fast/css/word-spacing-characters-complex-text.html
imported/csswg-test/css-writing-modes-3/text-orientation-script-001m.html
virtual/antialiasedtext/fast/text/zero-width-characters-complex-script.html
fast/text/zero-width-characters-complex-script.html
fast/text/trailing_whitespace_wrapping.html.