Use BBH reserve hook to preallocate space for tiles.

Use BBH reserve hook to preallocate space for tiles.

Before getting too far into changing how SkTileGrid stores its tiles, I figured I'd
better see how much I can tweak out the existing format.  Cleverly, that way
any improvements I make by changing the format will look that much less
impressive.

This CL looks like it will be a 5-15% win in time spent recording, with no effect
on playback.

This CL also shrinks the tiles to fit exactly when we're done inserting,
using newly added SkTDArray::shrinkToFit().  It's quite cheap to run (maybe
taking back 1-2% from those 5-15% wins), and means we'll lug around about 15%
fewer bytes in the tile grids.  Note though this strategy temporarily uses up to
30% more memory while building the tile grid.  For our largest SKPs, that's 
maybe 75-100K extra.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/52455cbc02d7f480d988ae7cdacc11ad69078c2c

CQ_EXTRA_TRYBOTS=tryserver.skia:Canary-Chrome-Ubuntu13.10-Ninja-x86_64-ToT-Trybot

Committed: https://skia.googlesource.com/skia/+/092dab98220110e7244ccbbb851efa8ad621ab88

[mtklein, 2014-10-09 19:00:37]

mtklein@google.com changed reviewers:
+ mtklein@google.com, reed@google.com, robertphillips@google.com

[mtklein, 2014-10-09 19:00:37]

mtklein@google.com changed required reviewers:
+ reed@google.com

[reed1, 2014-10-09 19:08:04]

lgtm

[mtklein, 2014-10-09 19:08:32]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-10-09 19:09:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/639823005/80001

[commit-bot: I haz the power, 2014-10-09 19:37:04]

Committed patchset #2 (id:80001) as 52455cbc02d7f480d988ae7cdacc11ad69078c2c

[mtklein, 2014-10-09 20:54:41]

A revert of this CL (patchset #2 id:80001) has been created in
https://codereview.chromium.org/642933002/ by mtklein@google.com.

The reason for reverting is: failed assertion "fXTiles * fYTiles != 0".

[mtklein, 2014-10-09 23:48:11]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-10-09 23:49:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/639823005/190001

[commit-bot: I haz the power, 2014-10-10 01:22:45]

Committed patchset #3 (id:190001) as 092dab98220110e7244ccbbb851efa8ad621ab88