Fix paint invalidation and painting for composited-scrolling input elements.

Fix paint invalidation and painting for composited-scrolling input elements.

In, particular, the following issues:

1. Paint invalidation missed cases when elements had "intrinsic scrollability",
in particular input elements.
2. Invalidation of carets incorrectly included scrolling for composited input
elements.
3. The DisplayItemClient must be distinct for case #2, because it paints into
a different GraphicsLayer than the rest of the LayoutBlock.

BUG=635724
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2271883002
Cr-Commit-Position: refs/heads/master@{#415013}
(cherry picked from commit b1d694f3370e4b6d6e723382c086617f85c94e93)

Committed: https://chromium.googlesource.com/chromium/src/+/096f5bf603212251bff19486f9d487e0c8a4f123

[chrishtr, 2016-08-29 22:58:22]

Description was changed from

==========
Fix paint invalidation and painting for composited-scrolling input elements.

In, particular, the following issues:

1. Paint invalidation missed cases when elements had "intrinsic scrollability",
in particular input elements.
2. Invalidation of carets incorrectly included scrolling for composited input
elements.
3. The DisplayItemClient must be distinct for case #2, because it paints into
a different GraphicsLayer than the rest of the LayoutBlock.

BUG=635724
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2271883002
Cr-Commit-Position: refs/heads/master@{#415013}
(cherry picked from commit b1d694f3370e4b6d6e723382c086617f85c94e93)
==========

to

==========
Fix paint invalidation and painting for composited-scrolling input elements.

In, particular, the following issues:

1. Paint invalidation missed cases when elements had "intrinsic scrollability",
in particular input elements.
2. Invalidation of carets incorrectly included scrolling for composited input
elements.
3. The DisplayItemClient must be distinct for case #2, because it paints into
a different GraphicsLayer than the rest of the LayoutBlock.

BUG=635724
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2271883002
Cr-Commit-Position: refs/heads/master@{#415013}
(cherry picked from commit b1d694f3370e4b6d6e723382c086617f85c94e93)

Committed:
https://chromium.googlesource.com/chromium/src/+/096f5bf603212251bff19486f9d4...
==========

[chrishtr, 2016-08-29 22:58:24]

Committed patchset #1 (id:1) manually as
096f5bf603212251bff19486f9d487e0c8a4f123.