Revert of Souped-up SkTextBlob.

Revert of Souped-up SkTextBlob. (patchset #3 id:40001 of https://codereview.chromium.org/581173003/)

Reason for revert:
Broke the new blobshader gm.

Original issue's description:
> Souped-up SkTextBlob.
> 
> Refactored text blob backend for improved performance: instead of using
> separate buffers for runs/positions/glyphs, everything is now packed in
> a consolidated slab (including the SkTextBlob object itself!).
> 
> Benefits:
> 
>  * number of allocations per blob construction reduced from ~4 to 1
>    (also minimizes internal fragmentation)
>  * run record size reduced by 8 bytes
> 
> This takes the blob construction overhead down to negligible levels
> (for the current Blink uncached textblob implementation).
> 
> Unfortunately, the code is much more finicky (run merging in
> particular) -- hence the assert spree.
> 
> Multi-run blobs are vulnerable to realloc storms but this is not a
> problem at the moment because Blink is using one-run blobs 99% of the
> time. Will be addressed in the future.
> 
> 
> R=reed@google.com,mtklein@google.com,robertphillips@google.com
> 
> Committed: https://skia.googlesource.com/skia/+/13645ea0ea87038ebd71be3bd6d53b313069a9e4

TBR=mtklein@google.com,reed@google.com,robertphillips@google.com
NOTREECHECKS=true
NOTRY=true

Committed: https://skia.googlesource.com/skia/+/e50215e5988c3b29c3e337fdd7cc3c9b13cec013

[f(malita), 2014-09-20 02:02:25]

Created Revert of Souped-up SkTextBlob.

[commit-bot: I haz the power, 2014-09-20 02:03:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/588853002/1

[commit-bot: I haz the power, 2014-09-20 02:03:09]

Committed patchset #1 (id:1) as e50215e5988c3b29c3e337fdd7cc3c9b13cec013