Fix premature termination of scroll animations while selecting text.

Fix premature termination of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a very small
(< 1px) non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
Committed: https://crrev.com/67a7b9d7646d67829d2991376cef8462ff4c6071
Cr-Commit-Position: refs/heads/master@{#380162}

[skobes, 2016-03-09 00:39:28]

Description was changed from

==========
Fix premature cancellation of scroll animations during text selection.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting the scroll animator before it could finish a user scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a small
non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

to

==========
Fix premature cancellation of scroll animations during text selection.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a small
non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

[skobes, 2016-03-09 00:39:43]

Description was changed from

==========
Fix premature cancellation of scroll animations during text selection.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a small
non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

to

==========
Fix premature cancellation of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a small
non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

[skobes, 2016-03-09 00:40:02]

Description was changed from

==========
Fix premature cancellation of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a small
non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

to

==========
Fix premature termination of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a small
non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

[skobes, 2016-03-09 00:41:23]

Description was changed from

==========
Fix premature termination of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a small
non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

to

==========
Fix premature termination of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a very small
(< 1px) non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

[skobes, 2016-03-09 00:43:13]

skobes@chromium.org changed reviewers:
+ bokan@chromium.org

[bokan, 2016-03-09 18:34:38]

lgtm

[skobes, 2016-03-09 18:35:26]

The CQ bit was checked by skobes@chromium.org

[commit-bot: I haz the power, 2016-03-09 18:35:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1775213002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1775213002/1

[commit-bot: I haz the power, 2016-03-09 18:44:21]

Description was changed from

==========
Fix premature termination of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a very small
(< 1px) non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

to

==========
Fix premature termination of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a very small
(< 1px) non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

[commit-bot: I haz the power, 2016-03-09 18:44:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-03-09 18:45:27]

Description was changed from

==========
Fix premature termination of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a very small
(< 1px) non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918
==========

to

==========
Fix premature termination of scroll animations while selecting text.

During text selection, AutoscrollController calls scrollIntoView continuously
to make the scroll position follow the selection.  This had the side effect of
resetting ScrollAnimator before it could finish a main-thread smooth scroll.

There are early returns for zero-delta scrolls in FrameView::setScrollPosition
and RootFrameViewport::distributeScrollBetweenViewports, but scrollIntoView's
conversion of fractional scroll offsets to LayoutUnits resulted in a very small
(< 1px) non-zero scroll delta.

We now avoid this by directly comparing the input and output of getRectToExpose
and skipping the unneeded calls to setScrollPosition.

BUG=591918

Committed: https://crrev.com/67a7b9d7646d67829d2991376cef8462ff4c6071
Cr-Commit-Position: refs/heads/master@{#380162}
==========

[commit-bot: I haz the power, 2016-03-09 18:45:28]

Patchset 1 (id:??) landed as
https://crrev.com/67a7b9d7646d67829d2991376cef8462ff4c6071
Cr-Commit-Position: refs/heads/master@{#380162}