Account for scroll origin in scroll animators.

Account for scroll origin in scroll animators.

Blink and cc have different notions of scroll offset - Blink's is relative to
the scroll origin which is non-zero in RTL documents.

The CompositorScrollOffsetAnimationCurve must work entirely in cc scroll offsets
since it is handed over to cc which doesn't know about the scroll origin.

This patch teaches ScrollAnimator and ProgrammaticScrollAnimator to convert in
both directions when creating and using the curve object.

BUG=593186
Review URL: https://codereview.chromium.org/1776503002

Cr-Commit-Position: refs/heads/master@{#379974}
(cherry picked from commit 0bb16600006793953292ee1e7fd8bf0a66f575dc)

Committed: https://chromium.googlesource.com/chromium/src/+/484078e368c1718cc3b1508931eb6b9f5e561fd5

[skobes, 2016-03-10 19:43:43]

Description was changed from

==========
Account for scroll origin in scroll animators.

Blink and cc have different notions of scroll offset - Blink's is relative to
the scroll origin which is non-zero in RTL documents.

The CompositorScrollOffsetAnimationCurve must work entirely in cc scroll offsets
since it is handed over to cc which doesn't know about the scroll origin.

This patch teaches ScrollAnimator and ProgrammaticScrollAnimator to convert in
both directions when creating and using the curve object.

BUG=593186

Review URL: https://codereview.chromium.org/1776503002

Cr-Commit-Position: refs/heads/master@{#379974}
(cherry picked from commit 0bb16600006793953292ee1e7fd8bf0a66f575dc)
==========

to

==========
Account for scroll origin in scroll animators.

Blink and cc have different notions of scroll offset - Blink's is relative to
the scroll origin which is non-zero in RTL documents.

The CompositorScrollOffsetAnimationCurve must work entirely in cc scroll offsets
since it is handed over to cc which doesn't know about the scroll origin.

This patch teaches ScrollAnimator and ProgrammaticScrollAnimator to convert in
both directions when creating and using the curve object.

BUG=593186

Review URL: https://codereview.chromium.org/1776503002

Cr-Commit-Position: refs/heads/master@{#379974}
(cherry picked from commit 0bb16600006793953292ee1e7fd8bf0a66f575dc)

Committed:
https://chromium.googlesource.com/chromium/src/+/484078e368c1718cc3b1508931eb...
==========

[skobes, 2016-03-10 19:43:44]

Committed patchset #1 (id:1) manually as
484078e368c1718cc3b1508931eb6b9f5e561fd5 (tree was closed).