Repro steps:

1. Turn on dictation (either from settings or the status bar)
2. Go to chrome://flags and toggle any flag (and restart)
3. Try to toggle dictation from the status bar > Accessibility

Expected: feature toggles on and off
Actual: feature remains off

Edit: Restarting without toggling a flag also appears to cause the issue

Thanks, Zach! I can repro with both the flags and with simply restarting. I'll update the description above with clear steps. 

 Issue 866519  has been merged into this issue.

Note for future: when verifying this bug after it is fixed, please also consider the steps outlined in  Issue 866519  for use with ChromeVox

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/139fb9b517de2eacc2a057433ccced086aa5f7a7

commit 139fb9b517de2eacc2a057433ccced086aa5f7a7
Author: Zach Helfinstein <zhelfins@chromium.org>
Date: Thu Jul 26 23:11:42 2018

Fix dictation pref not updating

Bug:  865260 
Change-Id: Ied9a9068518cdbc9e05a42cace066c110c0c0e05
Reviewed-on: https://chromium-review.googlesource.com/1147494
Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Katie Dektar <katie@chromium.org>
Commit-Queue: Zach Helfinstein <zhelfins@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578476}
[modify] https://crrev.com/139fb9b517de2eacc2a057433ccced086aa5f7a7/ash/accessibility/accessibility_controller.cc

Google Chrome	70.0.3505.0 (Official Build) canary (64-bit)
Firmware Version	Google_Eve.9584.160.0

Tested and verified using the above steps plus these steps:

Enable dictation, change a flag at chrome://flags, then restart per the prompt. Dictation stays on and there are no issues with turning it off and on from the status menu. Pass

Toggle the setting off and on in the status menu while watching the Settings > Manage Accessibility Settings page to ensure that dictation also turns off and on. Pass. Do the reverse, toggle off and on from the settings page, ensure that the status bar menu updates. Pass. 

Your change meets the bar and is auto-approved for M69. Please go ahead and merge the CL to branch 3497 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), kariahda@(iOS), cindyb@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/37291053a94a494bb9d8b78f07b18c26e95356b8

commit 37291053a94a494bb9d8b78f07b18c26e95356b8
Author: Zach Helfinstein <zhelfins@chromium.org>
Date: Wed Aug 01 19:22:47 2018

Fix dictation pref not updating

TBR=zhelfins@chromium.org

(cherry picked from commit 139fb9b517de2eacc2a057433ccced086aa5f7a7)

Bug:  865260 
Change-Id: Ied9a9068518cdbc9e05a42cace066c110c0c0e05
Reviewed-on: https://chromium-review.googlesource.com/1147494
Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Katie Dektar <katie@chromium.org>
Commit-Queue: Zach Helfinstein <zhelfins@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#578476}
Reviewed-on: https://chromium-review.googlesource.com/1158799
Cr-Commit-Position: refs/branch-heads/3497@{#318}
Cr-Branched-From: 271eaf50594eb818c9295dc78d364aea18c82ea8-refs/heads/master@{#576753}
[modify] https://crrev.com/37291053a94a494bb9d8b78f07b18c26e95356b8/ash/accessibility/accessibility_controller.cc