Fixed scrolling for mixed-valuator mouse

Fixed scrolling for mixed-valuator mouse

I fixed scrolling for the case when a mouse only has a scroll valuator for one
of its axes; this is done by first making GetScrollOffsetsFromXEvent only
return true when an actual smooth scroll event is being processed, and secondly
by adding a second check that disables legacy scroll events if the device could
have outputted a valuator event.

BUG=596013
Review URL: https://codereview.chromium.org/1891303002

Cr-Commit-Position: refs/heads/master@{#389059}
(cherry picked from commit 1517f16eda05f6cbec46cb9efdf806ce7ed2240c)

Committed: https://chromium.googlesource.com/chromium/src/+/6433bb28a72791a3ab62e854b4b16a5cdd03db2f

[dtapuska, 2016-04-28 20:50:30]

Description was changed from

==========
Fixed scrolling for mixed-valuator mouse

I fixed scrolling for the case when a mouse only has a scroll valuator for one
of its axes; this is done by first making GetScrollOffsetsFromXEvent only
return true when an actual smooth scroll event is being processed, and secondly
by adding a second check that disables legacy scroll events if the device could
have outputted a valuator event.

BUG=596013

Review URL: https://codereview.chromium.org/1891303002

Cr-Commit-Position: refs/heads/master@{#389059}
(cherry picked from commit 1517f16eda05f6cbec46cb9efdf806ce7ed2240c)
==========

to

==========
Fixed scrolling for mixed-valuator mouse

I fixed scrolling for the case when a mouse only has a scroll valuator for one
of its axes; this is done by first making GetScrollOffsetsFromXEvent only
return true when an actual smooth scroll event is being processed, and secondly
by adding a second check that disables legacy scroll events if the device could
have outputted a valuator event.

BUG=596013

Review URL: https://codereview.chromium.org/1891303002

Cr-Commit-Position: refs/heads/master@{#389059}
(cherry picked from commit 1517f16eda05f6cbec46cb9efdf806ce7ed2240c)

Committed:
https://chromium.googlesource.com/chromium/src/+/6433bb28a72791a3ab62e854b4b1...
==========

[dtapuska, 2016-04-28 20:50:31]

Committed patchset #1 (id:1) manually as
6433bb28a72791a3ab62e854b4b16a5cdd03db2f.