Drop event should generate user gesture.

Drop event should generate user gesture.

Generate a user gesture when drop event is fired. This is useful for extensions
to call some user gesture based APIs during a drop event. Please see the bug
for a sample extension.

R=adamk@chromium.org,abarth@chromium.org
BUG=355269
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170079

[wjywbs, 2014-03-22 19:35:44]

PTAL. Thanks.

[abarth-chromium, 2014-03-24 03:51:28]

https://codereview.chromium.org/208853006/diff/1/Source/core/page/DragControl...
File Source/core/page/DragController.cpp (right):

https://codereview.chromium.org/208853006/diff/1/Source/core/page/DragControl...
Source/core/page/DragController.cpp:238: bool
DragController::performDrag(DragData* dragData)
Are you sure this can't be triggered by script?

[wjywbs, 2014-03-24 12:14:10]

https://codereview.chromium.org/208853006/diff/1/Source/core/page/DragControl...
File Source/core/page/DragController.cpp (right):

https://codereview.chromium.org/208853006/diff/1/Source/core/page/DragControl...
Source/core/page/DragController.cpp:238: bool
DragController::performDrag(DragData* dragData)
On 2014/03/24 03:51:29, abarth wrote:
> Are you sure this can't be triggered by script?
I tried to use script to trigger this function and I added a log, but this
function wasn't run. I believe this is not the code path to dispatch drop event
in script:

var event = document.createEvent("HTMLEvents");
event.initEvent("drop",true,true);
document.getElementById("div1").dispatchEvent(event);

[abarth-chromium, 2014-03-24 16:34:35]

On 2014/03/24 12:14:10, wjywbs wrote:
> I tried to use script to trigger this function and I added a log, but this
> function wasn't run. I believe this is not the code path to dispatch drop
event
> in script:
> 
> var event = document.createEvent("HTMLEvents");
> event.initEvent("drop",true,true);
> document.getElementById("div1").dispatchEvent(event);

Hum...  We should study the code more to make sure that's the case.  The biggest
risk from this CL is that we introduce a way to bypass the popup blocker.

[wjywbs, 2014-03-25 11:49:05]

Here's some of my study of drop event dispatching:

When dispatching events from script like this:
    document.getElementById("div1").dispatchEvent(event)

It goes through dispatchEventMethod in
out/Debug/gen/blink/bindings/V8EventTarget.cpp line 171 and directly calling
EventTarget::dispatchEvent

When dragging elements with mouse, it runs EventHandler::dispatchDragEvent to
EventTarget::dispatchEvent.

When dropping elements with mouse, it runs DragController::performDrag ->
EventHandler::performDragAndDrop -> EventHandler::dispatchDragEvent ->
EventTarget::dispatchEvent.

When running ondrop event like this:
    document.getElementById("div1").ondrop = drop;
    document.getElementById("div1").ondrop(event);
It doesn't go to dispatchEventMethod in V8EventTarget or any drop handlers above
like DragController::performDrag or EventHandler::performDragAndDrop. It goes to
EventTarget::dispatchEvent, but I haven't found which function called it.

Hopefully this helps.

[abarth-chromium, 2014-03-25 15:26:51]

On 2014/03/25 11:49:05, wjywbs wrote:
> Hopefully this helps.

Tracing back the call chain via cs.chromium.org, the call chain comes from
WebContentsViewAura::OnPerformDrop, which probably means it's ok.

As far as I can tell, the only caller of this function is
WebViewImpl::dragTargetDrop, which is a better place to add the user gesture
indicator because it's rare for DOM code to call into WebView API functions.

[abarth-chromium, 2014-03-25 15:27:06]

Also, please add a test.  You can trigger this code path from the EventSender.

[wjywbs, 2014-03-26 16:14:14]

I moved the user gesture indicator to WebViewImpl::dragTargetDrop, and I added a
test. PTAL, and thanks for mentoring.

[abarth-chromium, 2014-03-26 16:50:22]

lgtm

Perfect.  Thanks!

[commit-bot: I haz the power, 2014-03-26 16:50:31]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wjywbs@gmail.com/208853006/40001

[commit-bot: I haz the power, 2014-03-26 16:53:07]

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

[commit-bot: I haz the power, 2014-03-26 16:53:12]

Try jobs failed on following builders:
  tryserver.blink on blink_presubmit

[abarth-chromium, 2014-03-26 16:58:46]

The CQ bit was checked by abarth@chromium.org

[commit-bot: I haz the power, 2014-03-26 16:58:52]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/wjywbs@gmail.com/208853006/40001

[commit-bot: I haz the power, 2014-03-26 18:04:01]

Change committed as 170079