This is a known issue already reported here and fixed in Chrome 67, if I'm not mistaken.

Able to reproduce the issue on reported version 66.0.3359.139 and latest stable# 66.0.3359.170 and the same is not seen on Beta# 67.0.3396.40 and latest canary 68.0.3429.0 using Mac 10.12.6, hence providing reverse bisect info
Note: Issue is not applicable to Windows 10 & Ubuntu 14.04
Reverse Bisect Info:
================
Last Bad build: 67.0.3362.0
First Good build: 67.0.3364.0

You are probably looking for a change made after 540879 (known good), but no later than 540880 (first known bad).
https://chromium.googlesource.com/chromium/src/+log/7bea94e12121bc43c45d68779803b5628f7ebbf1..a0259b3ae165b0673416f02848bed75082d639f4
Reviewed-on: https://chromium-review.googlesource.com/941883

@Robert Liao: Please confirm the issue and help in re-assigning if it is not related to your change, please help in merging it to M-66 if applicable
Adding ReleaseBlock-Stable for M-66, feel free to remove it if not applicable.

Thanks!

On Chrome 67 there is no popup animation at all. I've seen it in Canary, but decided to not report as far as it seemed so obvious.

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	chrome-67-no-popup-animation.mov 6.0 MB View Download

I've discovered related issues
https://bugs.chromium.org/p/chromium/issues/detail?id=428044
https://bugs.chromium.org/p/chromium/issues/detail?id=813371

In my case I'm dynamically adding adding borders at left at right due to borders inconsistency per Chrome version and operating system https://bugs.chromium.org/p/chromium/issues/detail?id=750419

I would be glad to represent my vision of how the popup should animate.

The popup animations has been removed with the move to the new UI Platform. Is my interpretation correct that this is no longer an issue on M67?

Shows up correctly near tip of tree. Waiting for feedback and will reelevate the priority if necessary.

So, here is a chronology as far as I understand:

1. Bug with blurred extension popup was found https://bugs.chromium.org/p/chromium/issues/detail?id=824963
2. The quick solution for 67 stable release was to revert the whole work on popups for several months, both for Chrome and Windows.
3. Now there is no popup animation on Mac, horizontal popup borders appear on Windows https://bugs.chromium.org/p/chromium/issues/detail?id=750419

So, I guess, that the work on popups will be continued, animation will be enabled and the bug with cropped content will appear again. Please, let us know when it happens, because I would like to submit some more popup animation issues for Mac and Windows.

In the near term, there will not be a resize animation for the popup dialog. Having said that, is there a version of your extension that demonstrates the reported bug?

@robliao No, I cannot reproduce it.

I'm going to mark this as WontFix then per #12 as there is no further work to be done here. If there is, feel free to comment/reopen.