[#7] Resubmitted - Pass gfx structs by const ref (gfx::Size)

[#7] Resubmitted - Pass gfx::Size by const ref.

(This patch is resubmitted as the earlier patch
http://crrev.com/145313006 got reverted due to build break
on linux_asan.)

Any struct of size > 4 bytes should be passed by const ref. 
Passing by ref for these structs is faster than passing by value,
especially when invoking function has multiple parameters and some
other scenarios mentioned in the bug.

BUG=159273

[prashant.n, 2014-01-28 15:07:00]

PTAL

[danakj, 2014-01-28 16:42:05]

Can you either

a) Upload the original patch here, then upload the changes so we can see the
diff.

or

b) Reopen the original CL and upload the changes there so we can see the diff
(without a rebase included in the changes please).

[prashant.n, 2014-01-29 11:19:57]

Please don't review this CL. I've modified original CL for the changes.