commit 2eec314f52989e78e862da1675b0d095e9629197
author Xida Chen <xidachen@chromium.org> Thu Jun 07 11:42:42 2018
committer Commit Bot <commit-bot@chromium.org> Thu Jun 07 11:42:42 2018
tree 73c42dea079b186d936b71744dc1f1be6233f62a
parent 4acf0b580ea8cb8a4763d97dc8a77a4da959e0cb

Reland of: Make TouchActionFilter::allowed_touch_action_ optional

The original CL was reverted because of multiple failures, this CL fixes
them one by one and lists them here. The first patch set is exactly the
same as the one that was reverted, so that it is easier to review.

1. crbug.com/845012
The original CL caused 3 tests to fail on multiple bots because of
a illegal downcast from MockInputRouter to InputRouter. PS#3 should
have that fixed.

2. crbug.com/845063, crbug.com/844858, crbug.com/845150
The problem is due to calling ResetTouchAction at GSE in cases that
it should not.
In a typical fling sequence, we have GSB, then a bunch of GSU, then
a FlingStart, then another bunch of GSU, and then a GSE. If we have a
in-flight fling and we start a second fling sequence before GSE of
the first fling, then OnSetTouchAction is called for the second
gesture sequence and that sets the |allowed_touch_action_|. After
that, GSE of the first fling comes which resets the |allowed_touch_action_|.
Then when the GSB of the second fling comes it doesn't have a valid
touch action to start with which results in the crash.

This is now fixed by using another member |scrolling_touch_action_|,
which takes over the value in the |allowed_touch_action_| when there
is a touch sequence end. So we reset the |allowed_touch_action_| at
each touch sequence end, and if that is not the gesture sequence end,
we will keep using the |scrolling_touch_action_| until the next TapDown.

3. crbug.com/845153
Tested this locally. The problem is JS injecting a touch event handler
in the middle of gesture sequence. In my original CL, when we saw a
touch event handler, we call ResetTouchAction(). If that happens in the
middle of a gesture sequence, then allowed_touch_action_ has no value
when subsequence gesture events comes which results in the crash.

This is also solved by using the |scrolling_touch_action_| which will
not be reset when JS inject a touch event handler.

TBR=pdr@chromium.org, piman@chromium.org

Bug: 845012, 845063, 844858, 845153, 845150
Change-Id: I4f1e1deff71db4587fb42c38f87ccb1cb7311cdc
Reviewed-on: https://chromium-review.googlesource.com/1068204
Commit-Queue: Xida Chen <xidachen@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565233}