Revert of "Change fallback font collection in HarfBuzzShaper"

Revert of "Change fallback font collection in HarfBuzzShaper" (patchset #1 id:1 of https://codereview.chromium.org/1229413005/)

Reason for revert:
Broke Linux MSAN bots on relanding:

http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20MSAN/builds/4448

==4==WARNING: MemorySanitizer: use-of-uninitialized-value
07:37:45.901 15833       #0 0x7fc50442fdbf in blink::ShapeResult::fallbackFonts(WTF::HashSet<blink::SimpleFontData const

seems to be the common complaint in the tests that broke.

Original issue's description:
> Reland of land "Change fallback font collection in HarfBuzzShaper" (patchset #1 id:1 of https://codereview.chromium.org/1235163007/)
> 
> Reason for revert:
> 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
> 
> 
> 
> Original issue's description:
> > 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
> 
> TBR=leviw@chromium.org,eae@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198951

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

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198964

[Noel Gordon, 2015-07-15 15:11:46]

Created Revert of "Change fallback font collection in HarfBuzzShaper"

[commit-bot: I haz the power, 2015-07-15 15:12:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1237283004/1

[commit-bot: I haz the power, 2015-07-15 15:13:23]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=198964