Implement <webview> droplink event

Implement <webview> droplink event

In the Chrome signin page, we expect it to be possible to navigate on dragging URLs
from outside of the content area into the content area. In <webview>, we do not wish
to navigate the <webview> on link drop but the embedder. Currently navigation on drop
is disabled within a <webview>. This CL provides a droplink event that the embedder can
listen to and navigate when a link is dropped into a <webview> from outside of its
bounds.

Note that this behavior is not identical to other Chrome tabs. In other tabs, if a link is dropped onto
a drop target, the page will not navigate. In this implementation, any external link drop will fire the droplink
event. This is probably not important for the signin
page however because no fields expect to take in links there. The plumbing in this patch
is less disruptive so I'll leave at that unless there is a pressing need to plumb the
navigation decision out of the guest Blink instance and up into the embedder.

BUG=460757
Committed: https://crrev.com/bdfc1ad220da363b6569f2a5632f52ff3520aef4
Cr-Commit-Position: refs/heads/master@{#317740}

[Fady Samuel, 2015-02-22 06:16:29]

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

[Fady Samuel, 2015-02-22 06:16:29]

Hi Istiaque, Roger,

Could you please take a look? As the description mentions, this behavior is not
identical to other Chrome tabs but it feels close enough to me. Thoughts?

Thanks,

Fady

[Roger Tawa OOO till Jul 10th, 2015-02-23 15:09:34]

lgtm for the behaviour.  I'll let lazyboy review the code.

[lazyboy, 2015-02-23 17:11:10]

https://chromiumcodereview.appspot.com/945333002/diff/1/content/browser/brows...
File content/browser/browser_plugin/browser_plugin_guest.cc (right):

https://chromiumcodereview.appspot.com/945333002/diff/1/content/browser/brows...
content/browser/browser_plugin/browser_plugin_guest.cc:683: dragged_url_ =
drop_data.url;
Just double checking, if the drop data doesn't have a url then it's an
empty GURL, right?

https://chromiumcodereview.appspot.com/945333002/diff/1/content/browser/brows...
content/browser/browser_plugin/browser_plugin_guest.cc:690:
owner_web_contents_->GetBrowserPluginEmbedder()->DragLeftGuest(this);
Also, change this to use |embedder|

https://chromiumcodereview.appspot.com/945333002/diff/1/content/public/browse...
File content/public/browser/browser_plugin_guest_delegate.h (right):

https://chromiumcodereview.appspot.com/945333002/diff/1/content/public/browse...
content/public/browser/browser_plugin_guest_delegate.h:54: // Notification that
a link was dropped over the guest.
Stress in the comment that |url| has to be valid (already).

[Fady Samuel, 2015-02-23 19:57:07]

PTAL Istiaque

https://codereview.chromium.org/945333002/diff/1/content/browser/browser_plug...
File content/browser/browser_plugin/browser_plugin_guest.cc (right):

https://codereview.chromium.org/945333002/diff/1/content/browser/browser_plug...
content/browser/browser_plugin/browser_plugin_guest.cc:683: dragged_url_ =
drop_data.url;
On 2015/02/23 17:11:10, lazyboy wrote:
> Just double checking, if the drop data doesn't have a url then it's an
> empty GURL, right?

Yup, the GURL is not valid, and spec() is empty string.

https://codereview.chromium.org/945333002/diff/1/content/browser/browser_plug...
content/browser/browser_plugin/browser_plugin_guest.cc:690:
owner_web_contents_->GetBrowserPluginEmbedder()->DragLeftGuest(this);
On 2015/02/23 17:11:10, lazyboy wrote:
> Also, change this to use |embedder|

Done.

https://codereview.chromium.org/945333002/diff/1/content/public/browser/brows...
File content/public/browser/browser_plugin_guest_delegate.h (right):

https://codereview.chromium.org/945333002/diff/1/content/public/browser/brows...
content/public/browser/browser_plugin_guest_delegate.h:54: // Notification that
a link was dropped over the guest.
On 2015/02/23 17:11:10, lazyboy wrote:
> Stress in the comment that |url| has to be valid (already).

Done.

[lazyboy, 2015-02-23 20:13:08]

lgtm

[Fady Samuel, 2015-02-23 20:15:25]

PTAL Charlie at content/public/browser_plugin_guest_delegate.h change. Thanks!

[Fady Samuel, 2015-02-23 21:32:10]

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

[Charlie Reis, 2015-02-23 23:29:50]

content/public/browser/browser_plugin_guest_delegate.h LGTM, but one question
about the approach:

How disruptive will this be if we end up using <webview> in other WebUI pages in
the future (beyond the sign-in case)?  I feel like this corner case will be easy
to forget about, leaving things like form field drag-n-drop broken for any new
use cases.  (Do we have any documented lists of assumptions and caveats about
using <webview> tags outside of apps?)

[Fady Samuel, 2015-02-23 23:35:37]

On 2015/02/23 23:29:50, Charlie Reis wrote:
> content/public/browser/browser_plugin_guest_delegate.h LGTM, but one question
> about the approach:
> 
> How disruptive will this be if we end up using <webview> in other WebUI pages
in
> the future (beyond the sign-in case)?  I feel like this corner case will be
easy
> to forget about, leaving things like form field drag-n-drop broken for any new
> use cases.  (Do we have any documented lists of assumptions and caveats about
> using <webview> tags outside of apps?)

Form field drag and drop still works fine. "Navigate on drop" is a browser
feature, not an HTML5 drag-and-drop feature.

[Fady Samuel, 2015-02-23 23:35:43]

The CQ bit was checked by fsamuel@chromium.org

[Fady Samuel, 2015-02-23 23:35:44]

The patchset sent to the CQ was uploaded after l-g-t-m from rogerta@chromium.org
Link to the patchset: https://codereview.chromium.org/945333002/#ps20001 (title:
"Addressed Istiaque's comments")

[commit-bot: I haz the power, 2015-02-23 23:37:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/945333002/20001

[commit-bot: I haz the power, 2015-02-24 00:01:19]

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

[commit-bot: I haz the power, 2015-02-24 00:01:20]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[Fady Samuel, 2015-02-24 00:03:09]

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

[Fady Samuel, 2015-02-24 00:03:09]

+xiyuan@ for authenticator.js

[xiyuan, 2015-02-24 00:04:15]

lgtm

[Fady Samuel, 2015-02-24 00:05:24]

The CQ bit was checked by fsamuel@chromium.org

[commit-bot: I haz the power, 2015-02-24 00:06:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/945333002/20001

[commit-bot: I haz the power, 2015-02-24 01:38:51]

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

[commit-bot: I haz the power, 2015-02-24 01:38:52]

Try jobs failed on following builders:
  android_chromium_gn_compile_dbg on tryserver.chromium.linux (JOB_TIMED_OUT, no
build URL)
Timed out jobs are not retried to avoid causing additional load on the builders
with large pending queues.

[Fady Samuel, 2015-02-24 01:59:15]

The CQ bit was checked by fsamuel@chromium.org

[commit-bot: I haz the power, 2015-02-24 02:00:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/945333002/20001

[commit-bot: I haz the power, 2015-02-24 02:10:26]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-24 02:11:17]

Patchset 2 (id:??) landed as
https://crrev.com/bdfc1ad220da363b6569f2a5632f52ff3520aef4
Cr-Commit-Position: refs/heads/master@{#317740}