gfx:: De-templatize Size and SizeF.

gfx:: De-templatize Size and SizeF.

This shrinks the android ChromeShell binary by 1076 bytes, and makes the
code easier for developers to read.

Performance-wise this change seems neutral (as opposed to the perf wins
from similar changes for Rect and Point classes). Performance numbers
are at http://crbug.com/407444#c19

R=sky
BUG=407444
Committed: https://crrev.com/adb045fd004834946c39bc11c24399ac4ebbac7c
Cr-Commit-Position: refs/heads/master@{#300285}

[sky, 2014-10-20 16:41:23]

LGTM

[danakj, 2014-10-20 16:42:18]

The CQ bit was checked by danakj@chromium.org

[commit-bot: I haz the power, 2014-10-20 16:43:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/662273002/20001

[commit-bot: I haz the power, 2014-10-20 17:12:51]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-10-20 17:14:05]

Patchset 2 (id:??) landed as
https://crrev.com/adb045fd004834946c39bc11c24399ac4ebbac7c
Cr-Commit-Position: refs/heads/master@{#300285}