Remove cached bounds in RenderLayer.

Remove cached bounds in RenderLayer.

This removes m_location, m_size, and m_offsetForInFlowPosition from RenderLayer, as well as the expensive layer tree walk that updates these fields during overflow scrolls.

BUG=400589
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179768

[abarth-chromium, 2014-08-07 21:51:13]

LGTM

There's some risk that not caching these values will make accumulating offsets
towards ancestors slower, but hopefully the perf bots will tell us about that.

It might be worth doing some diligence before landing this CL to check whether
we're causing that sort of regression...  Have you tried running the Silk
benchmark locally?

https://codereview.chromium.org/445263002/diff/40001/Source/core/rendering/Re...
File Source/core/rendering/RenderLayer.cpp (right):

https://codereview.chromium.org/445263002/diff/40001/Source/core/rendering/Re...
Source/core/rendering/RenderLayer.cpp:780: const IntSize RenderLayer::size()
const
No need for |const| here.  IntSize is a value type.

https://codereview.chromium.org/445263002/diff/40001/Source/core/rendering/Re...
Source/core/rendering/RenderLayer.cpp:792: const LayoutPoint
RenderLayer::location() const
No need for |const| here.  LayoutPoint is a value type.

[skobes, 2014-08-07 22:21:09]

I was also hoping to find some way of testing the perf impact of this change
before submitting it but I've been unsuccessful so far.

According to sullivan@ there is an issue with the perf trybots that requires a
change to tools/run-bisect-perf-regression.py to work around, but this file is
in the Chromium repo so I don't know how to make "git cl try" see that and my
Blink change at the same time.

I also tried running ./tools/perf/run_benchmark thread_times.key_silk_cases
locally but it gives me a CloudStorageError, not sure if that is expected or
not.

I think I am just going to land this and tell the perf sheriff to keep an eye on
things.

https://codereview.chromium.org/445263002/diff/40001/Source/core/rendering/Re...
File Source/core/rendering/RenderLayer.cpp (right):

https://codereview.chromium.org/445263002/diff/40001/Source/core/rendering/Re...
Source/core/rendering/RenderLayer.cpp:780: const IntSize RenderLayer::size()
const
On 2014/08/07 21:51:12, abarth wrote:
> No need for |const| here.  IntSize is a value type.

Done.

https://codereview.chromium.org/445263002/diff/40001/Source/core/rendering/Re...
Source/core/rendering/RenderLayer.cpp:792: const LayoutPoint
RenderLayer::location() const
On 2014/08/07 21:51:12, abarth wrote:
> No need for |const| here.  LayoutPoint is a value type.

Done.

[skobes, 2014-08-07 22:21:16]

The CQ bit was checked by skobes@chromium.org

[commit-bot: I haz the power, 2014-08-07 22:36:43]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/skobes@chromium.org/445263002/60001

[commit-bot: I haz the power, 2014-08-08 00:12:35]

Change committed as 179768