Revert of Reland "Change fallback font collection in HarfBuzzShaper"

Revert of Reland "Change fallback font collection in HarfBuzzShaper" (patchset #1 id:1 of https://codereview.chromium.org/1241613006/)

Reason for revert:
Broke Linux MSAN bots.

http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20MSAN/builds/4413

See stdio log of 4412 build: many reports use on an uninitialized variable in shaping font fallback, about 100+ tests failing that way.

Original issue's description:
> Reland "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.
> 
> Originally landed in r198813 (bbb929c88fbe43979dbb9b2b20218538) and then
> reverted in r198818 (64e30826c261ac7a2607e891dbe7e9d2d251e5f3) by virtue
> of Mac 10.6 test failures caused by a missing NULL check, since added.
> 
> This is a speculative fix.
> 
> R=leviw@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198886

TBR=leviw@chromium.org,eae@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198923

[Noel Gordon, 2015-07-15 04:36:34]

Created Revert of Reland "Change fallback font collection in HarfBuzzShaper"

[commit-bot: I haz the power, 2015-07-15 04:36:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1235163007/1

[commit-bot: I haz the power, 2015-07-15 04:37:31]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=198923

[Noel Gordon, 2015-07-15 12:14:58]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1229413005/ by noel@chromium.org.

The reason for reverting is: The breakage here was a side-effect of the change
that caused the problem [1].  Rolling this back in therefore.

[1] https://codereview.chromium.org/1234183003

.