[ios] Do not copy JS evaluation handlers before passing to WKWebView.

[ios] Do not copy JS evaluation handlers before passing to WKWebView.

WKWebView used to crash on deallocation when flushing scripts that
did not finish the execution but had a completion handler. This crash
has been fixed in iOS9, so this CL removes a crash workaround.

BUG=None

Committed: https://crrev.com/8a75e248a594471fbf75d84f404f9450e3fa3315
Cr-Commit-Position: refs/heads/master@{#358924}

[Eugene But (OOO till 7-30), 2015-11-10 19:08:00]

The CQ bit was checked by eugenebut@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-11-10 19:08:41]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1416743008/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1416743008/1

[commit-bot: I haz the power, 2015-11-10 19:31:47]

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

[commit-bot: I haz the power, 2015-11-10 19:31:47]

Dry run: This issue passed the CQ dry run.

[Eugene But (OOO till 7-30), 2015-11-10 21:28:13]

eugenebut@chromium.org changed reviewers:
+ shreyasv@chromium.org

[shreyasv1, 2015-11-10 21:34:04]

https://codereview.chromium.org/1416743008/diff/1/ios/web/web_state/ui/web_vi...
File ios/web/web_state/ui/web_view_js_utils.mm (right):

https://codereview.chromium.org/1416743008/diff/1/ios/web/web_state/ui/web_vi...
ios/web/web_state/ui/web_view_js_utils.mm:62: // deallocation, which will be
inefficient use of resources.
It's not clear what resource usage is being referred to here.

(Obviously) installing a completion handler when not needed is superfluous.
We can all agree to that.

This statement make it so that it also has to do with WKWebView deallocating
completion handlers on deallocation.
Also, I have never heard the term "flush" used with a completion handler. Do you
mean deallocated or purged?

[Eugene But (OOO till 7-30), 2015-11-10 21:44:05]

https://codereview.chromium.org/1416743008/diff/1/ios/web/web_state/ui/web_vi...
File ios/web/web_state/ui/web_view_js_utils.mm (right):

https://codereview.chromium.org/1416743008/diff/1/ios/web/web_state/ui/web_vi...
ios/web/web_state/ui/web_view_js_utils.mm:62: // deallocation, which will be
inefficient use of resources.
On 2015/11/10 21:34:04, shreyasv1 wrote:
> It's not clear what resource usage is being referred to here.
> 
> (Obviously) installing a completion handler when not needed is superfluous.
> We can all agree to that.
It's not only superfluous, it is actually more work for web view.

> This statement make it so that it also has to do with WKWebView deallocating
> completion handlers on deallocation.
> Also, I have never heard the term "flush" used with a completion handler. Do
you
> mean deallocated or purged?
No, I mean flushed (they are called with error before deallocation). Removed
this work from the comments.

Updated description. Please let me know if's still unclear why we prefer to pass
nil handlers.

[shreyasv1, 2015-11-10 21:45:09]

LGTM.

[Eugene But (OOO till 7-30), 2015-11-10 21:51:01]

Thanks for quick review!

[Eugene But (OOO till 7-30), 2015-11-10 21:51:05]

The CQ bit was checked by eugenebut@chromium.org

[commit-bot: I haz the power, 2015-11-10 21:51:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1416743008/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1416743008/20001

[commit-bot: I haz the power, 2015-11-10 22:06:55]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-11-10 22:07:37]

Patchset 2 (id:??) landed as
https://crrev.com/8a75e248a594471fbf75d84f404f9450e3fa3315
Cr-Commit-Position: refs/heads/master@{#358924}