WebView: speed up user gesture notification for GestureTap

WebView: speed up user gesture notification for GestureTap

Currently, when about to return, WebViewImpl::handleInputEvent notifies
Chromium if user gesture has been registered during event processing.

This notification comes too late when the first input event causes
a form submission, as explained in the code comment, and also in
http://crbug.com/372595#c13 .

This CL adds a special case handling for the only event with this problem:
GestureTap, so that this event is reported as a user gesture even before any
event handling takes place. This implements solution 1) from
http://crbug.com/372595#c14 .

BUG=372595
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=174337

[vabr (Chromium), 2014-05-16 19:22:07]

Hello Kent,

You helped me improve my recent code for password value unblocking in
https://codereview.chromium.org/235983016/, and I would really appreciate your
opinion here.

Questions:
Is it safe to assume that an input event of type GestureTap passed to
WebViewImpl::handleInputEvent will always result in a user gesture?
Do you see any drawbacks with the solution proposed here?

I'm aware that the CL lacks a test yet. I plan to add one which simulates the
original issue (taps on a submit button of a form, and observes if the password
value got transmitted). That should be easy to add on Chromium side, and I'll
think of a way to add it in Blink if possible. I won't land this CL without
having an approved test.

Thank you,
Vaclav

[tkent, 2014-05-18 23:32:32]

lgtm

[commit-bot: I haz the power, 2014-05-18 23:32:54]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/vabr@chromium.org/288423002/1

[commit-bot: I haz the power, 2014-05-19 05:33:31]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/7651)
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/7434)
  mac_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/8101)
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/8206)

[commit-bot: I haz the power, 2014-05-19 05:42:16]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-05-19 05:42:16]

Try jobs failed on following builders:
  mac_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/8106)

[vabr (Chromium), 2014-05-19 15:18:52]

Thank you, Kent.

Following the broken tests, I had to fix a NULL dereference and duplicated
reports of the user gesture in patch set 2.

Feel free to raise any objections. Given your approval with the first patch set,
and the simplicity of the change introduced in patch set 2, I plan to land this
tomorrow.

I'll implement the test for this fix in Chromium, because the test needs to have
the password manager working. The test is not finished yet, but I'll update this
CL with a link once it is.

Cheers,
Vaclav

[tkent, 2014-05-20 01:39:09]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2014-05-20 01:39:32]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/vabr@chromium.org/288423002/20001

[commit-bot: I haz the power, 2014-05-20 01:56:14]

Change committed as 174337

[vabr (Chromium), 2014-05-20 12:02:15]

Thanks!

For the record, the test for this fix is in
https://codereview.chromium.org/297693002/.