Work around PanGestureRecognizer iOS10 issue.

Work around PanGestureRecognizer iOS10 issue.

In iOS10, sometimes a PanGestureRecognizer will fire a touchesMoved even
after touchesBegan sets its state to |UIGestureRecognizerStateFailed|.
Somehow the state is re-set to UIGestureRecognizerStatePossible, and ends
up in moved.  Checking if |_startPoint| has been set is a secondary way to
catch for failed gestures. It appears setting failed in touchesMoved still always
works -- this issue only seems to be related to setting Failure in touchesBegan,
and only sometimes.

BUG=640611
Review-Url: https://codereview.chromium.org/2281303002
Cr-Commit-Position: refs/heads/master@{#415004}
(cherry picked from commit 95144337ab1af223377554b7ca838de787d8080e)

Committed: https://chromium.googlesource.com/chromium/src/+/50a444da0b655b362a1ae9d99345e6c78ae8a1d7

[justincohen, 2016-08-31 18:41:05]

Description was changed from

==========
Work around PanGestureRecognizer iOS10 issue.

In iOS10, sometimes a PanGestureRecognizer will fire a touchesMoved even
after touchesBegan sets its state to |UIGestureRecognizerStateFailed|.
Somehow the state is re-set to UIGestureRecognizerStatePossible, and ends
up in moved.  Checking if |_startPoint| has been set is a secondary way to
catch for failed gestures. It appears setting failed in touchesMoved still
always
works -- this issue only seems to be related to setting Failure in touchesBegan,
and only sometimes.

BUG=640611

Review-Url: https://codereview.chromium.org/2281303002
Cr-Commit-Position: refs/heads/master@{#415004}
(cherry picked from commit 95144337ab1af223377554b7ca838de787d8080e)
==========

to

==========
Work around PanGestureRecognizer iOS10 issue.

In iOS10, sometimes a PanGestureRecognizer will fire a touchesMoved even
after touchesBegan sets its state to |UIGestureRecognizerStateFailed|.
Somehow the state is re-set to UIGestureRecognizerStatePossible, and ends
up in moved.  Checking if |_startPoint| has been set is a secondary way to
catch for failed gestures. It appears setting failed in touchesMoved still
always
works -- this issue only seems to be related to setting Failure in touchesBegan,
and only sometimes.

BUG=640611

Review-Url: https://codereview.chromium.org/2281303002
Cr-Commit-Position: refs/heads/master@{#415004}
(cherry picked from commit 95144337ab1af223377554b7ca838de787d8080e)

Committed:
https://chromium.googlesource.com/chromium/src/+/50a444da0b655b362a1ae9d99345...
==========

[justincohen, 2016-08-31 18:41:07]

Committed patchset #1 (id:1) manually as
50a444da0b655b362a1ae9d99345e6c78ae8a1d7.