Articulate the cancel behavior in WebMouseWheelEvent.

Articulate the cancel behavior in WebMouseWheelEvent.

Add a DispatchType to mouse wheel events; set the cancelable flag
based on the dispatch type.

This change is similar to the one done for touch events
see https://codereview.chromium.org/1888163003/.

BUG=601661
Review URL: https://codereview.chromium.org/1894363004

Cr-Commit-Position: refs/heads/master@{#388643}
(cherry picked from commit 8050a57a2e31012caa7d0521a9be661491f8ef3d)

Committed: https://chromium.googlesource.com/chromium/src/+/0da211979aa69008d06680383c5f32f804ba632a

[dtapuska, 2016-04-22 14:01:18]

Description was changed from

==========
Articulate the cancel behavior in WebMouseWheelEvent.

Add a DispatchType to mouse wheel events; set the cancelable flag
based on the dispatch type.

This change is similar to the one done for touch events
see https://codereview.chromium.org/1888163003/.

BUG=601661

Review URL: https://codereview.chromium.org/1894363004

Cr-Commit-Position: refs/heads/master@{#388643}
(cherry picked from commit 8050a57a2e31012caa7d0521a9be661491f8ef3d)
==========

to

==========
Articulate the cancel behavior in WebMouseWheelEvent.

Add a DispatchType to mouse wheel events; set the cancelable flag
based on the dispatch type.

This change is similar to the one done for touch events
see https://codereview.chromium.org/1888163003/.

BUG=601661

Review URL: https://codereview.chromium.org/1894363004

Cr-Commit-Position: refs/heads/master@{#388643}
(cherry picked from commit 8050a57a2e31012caa7d0521a9be661491f8ef3d)

Committed:
https://chromium.googlesource.com/chromium/src/+/0da211979aa69008d06680383c5f...
==========

[dtapuska, 2016-04-22 14:01:20]

Committed patchset #1 (id:1) manually as
0da211979aa69008d06680383c5f32f804ba632a.