I've left this pretty late (it really should be in for M52 branch point). It's actually difficult from a design standpoint, as well as implementation (it has a very constrained framework for showing the UI). But it's also a very low visibility surface and will be deleted in M53 (hopefully), so we don't have to get it super perfect.

We can't easily remove the global setting checkbox while keeping the exceptions list.

My quick design proposal:
- On the main site settings view, Full screen always says "Allowed" underneath it.
- When you go into the fullscreen page, the Full screen global checkbox is shown checked, and underneath, it reads "Always allowed". (We brainstormed on this string, with dominickn@, and this was the best brief string we could come up with to explain to users that you can't change it.)
- Clicking the checkbox has no effect. You can't turn it off.
- All of the site exceptions are shown under the heading "Allowed". This allows you to view and individually reset the site settings you've previously put in for fullscreen.

Once again, all of this is necessary due to  Issue 591896 . We can't stop showing these settings until we delete the underlying data, and we can't do that until the new fullscreen UI is fully rolled out onto all platforms (which it will be in M52).

Attached current and proposed screenshots. (Oddly, finnur@ added that longer more specific string "Ask first before allowing sites to enter fullscreen (recommended)" a week ago, long after I removed that capability. :p)

Deleted: current-fullscreen-settings.png 51.5 KB

	current-fullscreen-settings.png 51.5 KB View Download

Deleted: proposed-fullscreen-settings.png 46.9 KB

	proposed-fullscreen-settings.png 46.9 KB View Download

CL (out for review): https://codereview.chromium.org/1989303005

I knew the FullScreen permission was slated for removal, but I added that string because I was asked to do a sweep of all the permissions and make the text permission-specific (each one communicate what it is that the toggle is changing). I didn't want FullScreen text to stand out, even for the small additional time that it would exist as UI element.

I also have some comments on the review.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/95e45b06eab6975d3a0be20b47b03c0aed6d176d

commit 95e45b06eab6975d3a0be20b47b03c0aed6d176d
Author: mgiuca <mgiuca@chromium.org>
Date: Thu May 19 23:39:42 2016

Added string "Always allowed" for Android content settings.

This will be used in a future CL to tell users that they cannot disable
the fullscreen permission. The string is being checked in early to
ensure it is in before branch point.

BUG= 611327 

Review-Url: https://codereview.chromium.org/1990153002
Cr-Commit-Position: refs/heads/master@{#394908}

[modify] https://crrev.com/95e45b06eab6975d3a0be20b47b03c0aed6d176d/chrome/android/java/strings/android_chrome_strings.grd

Awesome.

If the toggle doesn't do anything, should we grey it out so people understand that they can't do anything with it?

Blue = on so and grayed out = off so graying might not be enough... You could toast when the user taps it much like our "managed by your administrator" note. Something like "always allowed" just plain and simple for now, since it's only 1 milestone. Definitely try to make the next milestone because a lot of people don't update so this could be their reality for awhile. (And thought this is a small use case I do worry chrome-ui-review would block launch altogether, as they approved the toast but not this interim state. Depends on whether you have a launch bug. Mostly we don't want any of the Powers That Be being surprised to see the toggle not working. I could email them as an FYI if that's helpful.)

I see now in the code thread that finnur@ saw a way to disable the toggle altogether. That would be even better! No review needed for that I'd say.

#7/#8: I don't think we have a launch review. emilyschechter@ and I decided it was minimal enough to not warrant it (since we'd already had similar review on other platforms, and this was really just deleting a popup). However, I didn't realise we had this weird intermediate state where the setting still let you toggle even though it has no effect.

Looks like finnur@ has found a way to do it so I'll land that shortly.

Attaching screenshot of updated version with greyed out global toggle.

rolfe@: Now that it is disabled, it isn't clear we need the text "Always allowed". We could just keep the old "Allowed" and have it greyed out. WDYT?

Deleted: proposed-fullscreen-settings-update.png 44.7 KB

	proposed-fullscreen-settings-update.png 44.7 KB View Download

Well I'd say "always allowed" is pretty appropriate when you can't change the toggle! I'm fine either way though - you've been working with it the closest.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/827ed475ee038454ee7dfb2cadba17568fc4a2b5

commit 827ed475ee038454ee7dfb2cadba17568fc4a2b5
Author: mgiuca <mgiuca@chromium.org>
Date: Tue May 24 02:18:58 2016

Disable fullscreen global permission setting in Android.

Fixes a bug where fullscreen *looks* disableable but it's actually
always permitted by default. Forces the global slider to always be
turned on (the user cannot switch it to the off position), and changes
the string from "Allowed" to "Always allowed" to communicate that it
cannot be disabled.

This is a stop-gap measure until we can delete the data (and then this
setting UI will be removed entirely). See bug for details.

Only applies when the simplified-fullscreen-ui flag is enabled (which it
is by default).

BUG= 611327 

Review-Url: https://codereview.chromium.org/1989303005
Cr-Commit-Position: refs/heads/master@{#395513}

[modify] https://crrev.com/827ed475ee038454ee7dfb2cadba17568fc4a2b5/chrome/android/java/src/org/chromium/chrome/browser/preferences/website/ContentSettingsResources.java
[modify] https://crrev.com/827ed475ee038454ee7dfb2cadba17568fc4a2b5/chrome/android/java/src/org/chromium/chrome/browser/preferences/website/SingleCategoryPreferences.java
[modify] https://crrev.com/827ed475ee038454ee7dfb2cadba17568fc4a2b5/chrome/browser/android/preferences/pref_service_bridge.cc

Requesting merge of 827ed475ee038454ee7dfb2cadba17568fc4a2b5 / r395513 to M52. Rationale: in M52 we made the fullscreen setting do nothing. We need to disable the toggle so that users don't have an illusion of changing the setting that in fact does nothing.

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

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/73a4b14217bc2d96e41b80c1ec85b1478d96c383

commit 73a4b14217bc2d96e41b80c1ec85b1478d96c383
Author: Matt Giuca <mgiuca@chromium.org>
Date: Tue May 24 03:31:46 2016

Disable fullscreen global permission setting in Android.

Fixes a bug where fullscreen *looks* disableable but it's actually
always permitted by default. Forces the global slider to always be
turned on (the user cannot switch it to the off position), and changes
the string from "Allowed" to "Always allowed" to communicate that it
cannot be disabled.

This is a stop-gap measure until we can delete the data (and then this
setting UI will be removed entirely). See bug for details.

Only applies when the simplified-fullscreen-ui flag is enabled (which it
is by default).

BUG= 611327 

Review-Url: https://codereview.chromium.org/1989303005
Cr-Commit-Position: refs/heads/master@{#395513}
(cherry picked from commit 827ed475ee038454ee7dfb2cadba17568fc4a2b5)

Review URL: https://codereview.chromium.org/2006023005 .

Cr-Commit-Position: refs/branch-heads/2743@{#26}
Cr-Branched-From: 2b3ae3b8090361f8af5a611712fc1a5ab2de53cb-refs/heads/master@{#394939}

[modify] https://crrev.com/73a4b14217bc2d96e41b80c1ec85b1478d96c383/chrome/android/java/src/org/chromium/chrome/browser/preferences/website/ContentSettingsResources.java
[modify] https://crrev.com/73a4b14217bc2d96e41b80c1ec85b1478d96c383/chrome/android/java/src/org/chromium/chrome/browser/preferences/website/SingleCategoryPreferences.java
[modify] https://crrev.com/73a4b14217bc2d96e41b80c1ec85b1478d96c383/chrome/browser/android/preferences/pref_service_bridge.cc

Verified in M52-52.0.2743.8 build. attached the screenshot

Deleted: Screenshot_20160525-123552.png 56.5 KB

	Screenshot_20160525-123552.png 56.5 KB View Download