Move use of DisplayItemList's vector behind an explicit DisplayItems interface.

Move use of DisplayItemList's vector behind an explicit DisplayItems interface.

This is a step toward having an interface which can be implemented instead
by cc via WebDisplayItemList. In particular, the goal is to remove the
reliance on concrete blink::DisplayItem objects being stored.

BUG=484943
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196732

[jbroman, 2015-06-07 00:58:04]

Patchset #1 (id:1) has been deleted

[jbroman, 2015-06-07 00:58:17]

Patchset #1 (id:20001) has been deleted

[jbroman, 2015-06-08 19:26:31]

jbroman@chromium.org changed reviewers:
+ chrishtr@chromium.org, pdr@chromium.org

[jbroman, 2015-06-08 19:26:32]

This doesn't seem to have a perf impact, and if all goes well, will be replaced
soon by an implementation using WebDisplayItemList instead of storing a vector.

This abstraction should make it clear what kind of access to the paint list is
possible, so that the same thing can be written atop cc's representation, which
won't store OwnPtr<blink::DisplayItem> internally.

[chrishtr, 2015-06-08 23:03:05]

lgtm

https://codereview.chromium.org/1157653005/diff/80001/Source/platform/graphic...
File Source/platform/graphics/paint/DisplayItems.h (right):

https://codereview.chromium.org/1157653005/diff/80001/Source/platform/graphic...
Source/platform/graphics/paint/DisplayItems.h:38: // TODO(jbroman): Clarify the
purpose of this.
I agree, this method is pretty weird as named. What's the plan going forward?

[jbroman, 2015-06-09 00:00:02]

https://codereview.chromium.org/1157653005/diff/80001/Source/platform/graphic...
File Source/platform/graphics/paint/DisplayItems.h (right):

https://codereview.chromium.org/1157653005/diff/80001/Source/platform/graphic...
Source/platform/graphics/paint/DisplayItems.h:38: // TODO(jbroman): Clarify the
purpose of this.
On 2015/06/08 23:03:05, chrishtr wrote:
> I agree, this method is pretty weird as named. What's the plan going forward?

I think it's currently only used by the code that checks that cached display
items are used in appropriate cases.

The appropriate followup step would be to figure out whether we do want to have
a flag of this type, and if so, to have a boolean stored in Blink's sidecar data
to represent that state (something like m_usedByMergeAlgorithm).

Currently, this clears the OwnPtr holding the display item, hence the name
"gone" for now.

[jbroman, 2015-06-09 00:00:05]

The CQ bit was checked by jbroman@chromium.org

[commit-bot: I haz the power, 2015-06-09 00:00:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1157653005/80001

[commit-bot: I haz the power, 2015-06-09 03:04:29]

Committed patchset #3 (id:80001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=196732