The problem is caused by incorrect parameter of resizing the multiline cell. Submitting the fix on https://codereview.chromium.org/2094653003/ now.
Zach- could you nominate it for cherrypicking for M52? (or should I in the future just add the label by myself?) 

linux only bug. blocking the Translate2016Q2UI launch.

You can add it yourself too. :)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c4a16169021b1cc0c160d064ae6dfd0561a3e6b9

commit c4a16169021b1cc0c160d064ae6dfd0561a3e6b9
Author: ftang <ftang@chromium.org>
Date: Fri Jun 24 19:28:43 2016

fix the right padding problem of multiline text ("Do you want google to translate this page from LANG1 to LANG2") on Linux by allow horizontal resizing on the cell for the multi line label. See the problem screenshot on https://bugs.chromium.org/p/chromium/issues/detail?id=622327

BUG= 622327 

Review-Url: https://codereview.chromium.org/2094653003
Cr-Commit-Position: refs/heads/master@{#401928}

[modify] https://crrev.com/c4a16169021b1cc0c160d064ae6dfd0561a3e6b9/chrome/browser/ui/views/translate/translate_bubble_view.cc

Your change meets the bar and is auto-approved for M52 (branch: 2743)

Thank you ftang@ for providing the steps to verify this bug.

Verified this bug on Linux/Ubuntu 14.04 - Version 53.0.2780.0 dev (64-bit)
Please find the attached screenshot.

Steps:
1. Navigate to chrome://flags
2. Enable the flag "Translate 2016Q2 UI" and relaunch chrome.
3. Navigate to a website which shows up the translate bubble.
4. Verify the bubble and make sure text extends to the end before wrapping.

ftang@, can you please merge the CL in to M52 branch by EOD so that it gets picked up for Beta promotion scheduled this Wednesday.

Deleted: Translate Bubble.png 20.1 KB

	Translate Bubble.png 20.1 KB View Download

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/60fdce648e2e668b749266d0ff35cd3819cdefac

commit 60fdce648e2e668b749266d0ff35cd3819cdefac
Author: Rachel Blum <groby@google.com>
Date: Mon Jun 27 23:03:52 2016

fix the right padding problem of multiline text ("Do you want google to translate this page from LANG1 to LANG2") on Linux by allow horizontal resizing on the cell for the multi line label. See the problem screenshot on https://bugs.chromium.org/p/chromium/issues/detail?id=622327

BUG= 622327 

Review-Url: https://codereview.chromium.org/2094653003
Cr-Commit-Position: refs/heads/master@{#401928}
(cherry picked from commit c4a16169021b1cc0c160d064ae6dfd0561a3e6b9)

Review URL: https://codereview.chromium.org/2102793003 .

Cr-Commit-Position: refs/branch-heads/2743@{#491}
Cr-Branched-From: 2b3ae3b8090361f8af5a611712fc1a5ab2de53cb-refs/heads/master@{#394939}

[modify] https://crrev.com/60fdce648e2e668b749266d0ff35cd3819cdefac/chrome/browser/ui/views/translate/translate_bubble_view.cc

Tested the issue on Ubuntu 14.04 using 52.0.2743.60 as per steps in comment #6. Observed that the text extended to the end before wrapping.
Please find attached screenshot.

Marking it as TE-Verified.

Deleted: 622327.jpg 21.5 KB

	622327.jpg 21.5 KB View Download

This is working fine on Linux/Ubuntu 14.04 - Version 52.0.2743.60 beta (64-bit)

Deleted: Translate on Beta.png 23.8 KB

	Translate on Beta.png 23.8 KB View Download

Deleted: Translate on Beta second.png 12.1 KB

	Translate on Beta second.png 12.1 KB View Download