eugenebut@ could you please take a look

Vinutha, could you please bisect and find git revision of good and bad versions. git revision can be seen on chrome://version page.

Good Build - 58.0.3029.48Dev
Revision - 53f50337062b21a07e489e892ed7214201a61f89-refs/branch-heads/3029@{#528}

Bad Build- 58.0.3029.51dev
Revision - https://drive.google.com/open?id=0B6GVWQnhaMClZGN5Z3d6M1pFZWs

Thanks Vinutha. There were no functional changes in Chrome for iOS between 58.0.3029.48 and 58.0.3029.51. From the screenshot it looks like context menu was invoked for iframe, which never worked on iOS. Are you sure that you long pressing the same link? I tried to test context menu for an article in "News and buzz" section and everything works fine (iPad Air2, iOS 10.0, Chrome 58.0.3029.39 beta).

Vinutha, showed me this bug, which is not consistently reproducible. This is unrelated to iframes, but something that has actually regressed, because WebController.FetchContextMenuInfoAsyncSucceeded failure rate went up. 

This is very similar to crbug.com/542933. 

I am able to repro this bug consistently on webpages that are pre-rendered.
Steps to reproduce:
1.Launch app.
2.Load cnn.com or yahoo.com
3.Close the above launched website tabs.
4.Open new tab, type cn when the pre-rendered full website shows up in the omnibox tap on “Go” in keyboard.
5.Now Long press on any of the links to bring up the context menu.

Good Version - 58.0.3028.0 .
Good Version Revision - c49428ef69cfd173c5d7eaeb39982f44ca68da78-refs/heads/master@{#454140}
Link - https://drive.google.com/open?id=0B6GVWQnhaMClcnRHMGNpVDFVVkE 

Cannot test the bug for repro on 58.0.3029.0 because pre-rendering does not work - (https://bugs.chromium.org/p/chromium/issues/detail?id=698833)
Link - https://drive.google.com/open?id=0B6GVWQnhaMClM2F2QnFCXzhaeWc

Cannot test the bug for repro on 58.0.3029.39 dev because of crbug/698833
https://drive.google.com/open?id=0B6GVWQnhaMClN0JNcnEzYmNLT2M

Next testable build which it reproed on is 58.0.3029.48 dev
https://drive.google.com/open?id=0B6GVWQnhaMClOFc0QVhKYzdLV1k

I can repro with 58.0.3029.52 , but can't with 59.0.3064.0. Looks like this is branch only problem.

Fix on review: https://codereview.chromium.org/2804113005/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/817d8577b9790d3a0f3cbd2123446e5b2fcd577a

commit 817d8577b9790d3a0f3cbd2123446e5b2fcd577a
Author: eugenebut <eugenebut@chromium.org>
Date: Fri Apr 07 22:06:32 2017

Install delegates for preload Tab.

Cherry picked remaining part from
https://codereview.chromium.org/2759563003

uninstallDelegatesForTab does not exist on the branch and was not
copied.

BUG= 707970 
NOTRY=true
NOPRESUBMIT=true

Review-Url: https://codereview.chromium.org/2804113005
Cr-Commit-Position: refs/branch-heads/3029@{#635}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}

[modify] https://crrev.com/817d8577b9790d3a0f3cbd2123446e5b2fcd577a/ios/chrome/browser/ui/browser_view_controller.mm

Merge from comment 12 was a cherry-pick of cl/2759563003 which was approved for merge.

Verified the issue on the beta build 58.0.3029.67 tested on iPad Air(iOS10)
Open in Newtab option is available in context menu, works-fine.