BitmapImage: Use the cheapest Vector constructor.

BitmapImage: Use the cheapest Vector constructor.

Vector() and Vector(0) will result in the same object
but Vector() is cheaper (unless the optimizer manages
to optimize away everything in Vector(size_t) ).

BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181084

[Daniel Bratell, 2014-08-01 10:44:54]

senorblanco, could you please take a look at this trivial change. Just something
I stumbled upon while looking at Vector performance.

[Stephen White, 2014-08-04 14:59:20]

LGTM

Change seems harmless, but does this actually show up on any perf benchmarks?

[jamesr, 2014-08-07 17:38:30]

https://codereview.chromium.org/435913002/diff/1/Source/platform/graphics/Bit...
File Source/platform/graphics/BitmapImage.cpp (right):

https://codereview.chromium.org/435913002/diff/1/Source/platform/graphics/Bit...
Source/platform/graphics/BitmapImage.cpp:47: , m_frames()
why not just remove this line completely?

[Daniel Bratell, 2014-08-26 09:04:46]

On 2014/08/04 14:59:20, Stephen White wrote:
> LGTM
> 
> Change seems harmless, but does this actually show up on any perf benchmarks?

It did show up when profiling some tests but at a very low level. Maybe 0.1% or
less. I am looking at the code generation of Vector with gcc and it's not always
doing the optimal thing and when reading profiles I stumbled upon this more or
less by accident.

[Daniel Bratell, 2014-08-26 09:05:17]

https://codereview.chromium.org/435913002/diff/1/Source/platform/graphics/Bit...
File Source/platform/graphics/BitmapImage.cpp (right):

https://codereview.chromium.org/435913002/diff/1/Source/platform/graphics/Bit...
Source/platform/graphics/BitmapImage.cpp:47: , m_frames()
On 2014/08/07 17:38:29, jamesr wrote:
> why not just remove this line completely?

It is a question of style, but in the work I've been doing performance have been
noticeably affected by code in Vector constructors and destructors so I felt it
was beneficial to list all the work done when the constructor runs. But it's a
question of style so I don't have any strong opinions.

[Daniel Bratell, 2014-08-29 08:41:58]

The CQ bit was checked by bratell@opera.com

[commit-bot: I haz the power, 2014-08-29 08:42:43]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/bratell@opera.com/435913002/1

[commit-bot: I haz the power, 2014-08-29 09:47:18]

Committed patchset #1 (id:1) as 181084