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

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

Author: fmalita@chromium.org

Review URL: https://codereview.chromium.org/588853002
3 files changed