<webview>: make context menus cancellable using JS API

<webview>: make context menus cancellable using JS API.

Expose <webview>.contextMenus.onShow
chrome EventTarget like object so one can "addListener" that can
preventDefault() to cancel bringing up <webview> context menu.

BUG=465733
Test=Open a chrome app with <webview>. E.g.
Load a <webview> in a chrome app, e.g.
the browser sample app:
https://github.com/GoogleChrome/chrome-app-samples/tree/master/samples/webview-samples/browser

Right click on the <webview>, context menu is expected to be shown.

Now open the app's inspector: from chrome://inspect, switch to "Apps" then select to inspect "Browser sample".

Register a listener to disable context menu:

document.querySelector('webview').contextMenus.onShow.addListener(function(e) {
  e.preventDefault();
});

Right click on the <webview> again, context menu should not show up.

Committed: https://crrev.com/514286582142e26e93a09f5aeefb538259ad1f41
Cr-Commit-Position: refs/heads/master@{#322477}

[lazyboy, 2015-03-25 23:49:34]

lazyboy@chromium.org changed reviewers:
+ fsamuel@chromium.org

[lazyboy, 2015-03-25 23:49:34]

There's another easier route we can go though,
<webview>.addEventListener('some-name-for-onContextMenu', function(e) {
  e.preventDefault();
});
Problem with that approach is we're not using <webview>.contextMenus
object/namespace to keep all context menu related api-s together.

Now one potential issue with exposing <webview>.contextMenus.onContextMenu is we
cannot use addEventListener anymore because <webview>.contextMenus.onContextMenu
is not an EventTarget object. So I've used chrome's Event, therefore addListener
instead
of addEventListener. However we don't get default dom event behavior in this
case and I had to manually add "preventDefault" function on the event param
(see web_view_internal.json).
Let me know what you think, thanks.

[Fady Samuel, 2015-03-26 02:40:28]

This seems pretty reasonable to me. I have no objections. If you're comfortable
with it, I'll sign off on it.

https://codereview.chromium.org/1026383003/diff/40001/chrome/renderer/resourc...
File chrome/renderer/resources/extensions/web_view/chrome_web_view.js (right):

https://codereview.chromium.org/1026383003/diff/40001/chrome/renderer/resourc...
chrome/renderer/resources/extensions/web_view/chrome_web_view.js:160:
Object.defineProperty(
nit: $Object

[lazyboy, 2015-03-26 04:16:26]

1) My worry is if this somehow precludes us from using this event/function
in the future to implement contextMenus V2 API. To me it doesn't, so I think
this is fine.

As a note, re-using this in V2 API would be sth like:
<webview>.contextMenus.onContextMenu.addListener(function(e) {
  // e.items is the list/tree of items that is present in default context menu.
  var mutatedItems = ...;
  e.show(mutatedItems);
});

2) Other issue is subjective, this feels a bit long:
<webview>.contextMenus.onContextMenu.addListener(...);
compared to:
<webview>.addEventListener('willShowContextMenu', ..

https://chromiumcodereview.appspot.com/1026383003/diff/40001/chrome/renderer/...
File chrome/renderer/resources/extensions/web_view/chrome_web_view.js (right):

https://chromiumcodereview.appspot.com/1026383003/diff/40001/chrome/renderer/...
chrome/renderer/resources/extensions/web_view/chrome_web_view.js:160:
Object.defineProperty(
On 2015/03/26 02:40:28, Fady Samuel wrote:
> nit: $Object

Done.

[Fady Samuel, 2015-03-26 17:44:05]

On 2015/03/26 04:16:26, lazyboy wrote:
> 1) My worry is if this somehow precludes us from using this event/function
> in the future to implement contextMenus V2 API. To me it doesn't, so I think
> this is fine.
> 
> As a note, re-using this in V2 API would be sth like:
> <webview>.contextMenus.onContextMenu.addListener(function(e) {
>   // e.items is the list/tree of items that is present in default context
menu.
>   var mutatedItems = ...;
>   e.show(mutatedItems);
> });
> 

All you lose is capture and bubble, which is unfortunate but not horrible.


> 2) Other issue is subjective, this feels a bit long:
> <webview>.contextMenus.onContextMenu.addListener(...);
> compared to:
> <webview>.addEventListener('willShowContextMenu', ..
> 
>
https://chromiumcodereview.appspot.com/1026383003/diff/40001/chrome/renderer/...
> File chrome/renderer/resources/extensions/web_view/chrome_web_view.js (right):
> 
>
https://chromiumcodereview.appspot.com/1026383003/diff/40001/chrome/renderer/...
> chrome/renderer/resources/extensions/web_view/chrome_web_view.js:160:
> Object.defineProperty(
> On 2015/03/26 02:40:28, Fady Samuel wrote:
> > nit: $Object
> 
> Done.

What about <webview>.contextMenus.onShow.addListener(...)?

[lazyboy, 2015-03-26 19:18:02]

Comments addressed in patchset #5

https://chromiumcodereview.appspot.com/1026383003/diff/40001/chrome/renderer/...
File chrome/renderer/resources/extensions/web_view/chrome_web_view.js (right):

https://chromiumcodereview.appspot.com/1026383003/diff/40001/chrome/renderer/...
chrome/renderer/resources/extensions/web_view/chrome_web_view.js:160:
Object.defineProperty(
On 2015/03/26 04:16:26, lazyboy wrote:
> On 2015/03/26 02:40:28, Fady Samuel wrote:
> > nit: $Object
> 
> Done.

Renamed onContextMenu ->  onShow.
Renamed internal constant value to avoid confusion.

[Fady Samuel, 2015-03-26 19:21:11]

lgtm

[lazyboy, 2015-03-26 19:36:52]

lazyboy@chromium.org changed reviewers:
+ yoz@chromium.org

[lazyboy, 2015-03-26 19:36:52]

+Yoyo for OWNERS review:
chrome/common/extensions/api/chrome_web_view_internal.json

[Yoyo Zhou, 2015-03-26 19:50:44]

https://codereview.chromium.org/1026383003/diff/90001/chrome/common/extension...
File chrome/common/extensions/api/chrome_web_view_internal.json (right):

https://codereview.chromium.org/1026383003/diff/90001/chrome/common/extension...
chrome/common/extensions/api/chrome_web_view_internal.json:295: "description":
"Event fired when context menu is about to be shown, provides ability to cancel
context menu by preventDefault.",
Please rewrite this:

Fired when context menu is about to be shown. Provides the ability to...

actually I can't understand from reading this how to use preventDefault. Can you
elaborate on this?

[lazyboy, 2015-03-26 20:13:07]

https://codereview.chromium.org/1026383003/diff/90001/chrome/common/extension...
File chrome/common/extensions/api/chrome_web_view_internal.json (right):

https://codereview.chromium.org/1026383003/diff/90001/chrome/common/extension...
chrome/common/extensions/api/chrome_web_view_internal.json:295: "description":
"Event fired when context menu is about to be shown, provides ability to cancel
context menu by preventDefault.",
On 2015/03/26 19:50:44, Yoyo Zhou wrote:
> Please rewrite this:
> 
> Fired when context menu is about to be shown. Provides the ability to...
Done.
> 
> actually I can't understand from reading this how to use preventDefault. Can
you
> elaborate on this?
I've added "This can be done by calling event.preventDefault() ...".

[Yoyo Zhou, 2015-03-26 20:19:47]

LGTM

https://codereview.chromium.org/1026383003/diff/110001/chrome/common/extensio...
File chrome/common/extensions/api/chrome_web_view_internal.json (right):

https://codereview.chromium.org/1026383003/diff/110001/chrome/common/extensio...
chrome/common/extensions/api/chrome_web_view_internal.json:295: "description":
"Fired when context menu is about to be shown. Provides the ability to cancel
the context menu. This can be done by calling
<code>event.preventDefault()</code> from this handler.",
You can delete ". This can be done"

[lazyboy, 2015-03-26 20:32:21]

https://codereview.chromium.org/1026383003/diff/110001/chrome/common/extensio...
File chrome/common/extensions/api/chrome_web_view_internal.json (right):

https://codereview.chromium.org/1026383003/diff/110001/chrome/common/extensio...
chrome/common/extensions/api/chrome_web_view_internal.json:295: "description":
"Fired when context menu is about to be shown. Provides the ability to cancel
the context menu. This can be done by calling
<code>event.preventDefault()</code> from this handler.",
On 2015/03/26 20:19:47, Yoyo Zhou wrote:
> You can delete ". This can be done"

Done.

[lazyboy, 2015-03-26 21:41:20]

The CQ bit was checked by lazyboy@chromium.org

[lazyboy, 2015-03-26 21:41:20]

The patchset sent to the CQ was uploaded after l-g-t-m from
fsamuel@chromium.org, yoz@chromium.org
Link to the patchset:
https://chromiumcodereview.appspot.com/1026383003/#ps130001 (title: "address
comments from yoz@")

[commit-bot: I haz the power, 2015-03-26 21:41:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1026383003/130001

[commit-bot: I haz the power, 2015-03-26 21:45:28]

Committed patchset #8 (id:130001)

[commit-bot: I haz the power, 2015-03-26 21:46:23]

Patchset 8 (id:??) landed as
https://crrev.com/514286582142e26e93a09f5aeefb538259ad1f41
Cr-Commit-Position: refs/heads/master@{#322477}