eugenebut@, could you help triaging this? Not sure who to assign it to, or even if I should split it in multiple bugs.

Deleted: Simulator Screen Shot - iPhone SE - 2018-10-02 at 16.27.49.png 85.5 KB

	Simulator Screen Shot - iPhone SE - 2018-10-02 at 16.27.49.png 85.5 KB View Download

What is the status of Dynamic Type support in Chrome on iOS (do we support Dynamic Type on NTP and Settings)? Do we know if Android supports Dynamic type?

Interstitials are rendered HTML pages, so the fix should be interstitial specific, and ideally cross platform. 

Emily or Adrienne do you know who would be a good person to work on this? Asking you as owners of ios/chrome/browser/ssl

Android is supporting Dynamic Type on interstitials.

In Chrome on iOS, we are trying to support it. For now, not every screen is supporting it, but we should fix it.

+carlosil@ maybe can help us out?

carlosil@: ping

Sorry about the delay, this bug slipped through the cracks. I'm not sure I'm the right person to own this, since I'm not sure what Dynamic Type is :).

Is this something that needs to be changed in the HTML/CSS of the interstitial to support it? Or is this an ios thing separate from the interstitial. I'm happy to help with any interstitial changes that need to happen if I can be pointed to an example of other UI that supports this.

Dynamic Type is the iOS feature that allows the user to increase the font size for the different apps (same as Android "Font Size" option in display IIRC).

On Android, if you increase the font size, the font size of the HTML text in the interstitial is increasing. Do you know if it is something done by the interstitial or is it something more general on Android?

We already have FontSizeTabHelper(https://cs.chromium.org/chromium/src/ios/chrome/browser/web/font_size_tab_helper.h) which can adjust the font size in web pages by Javascript(https://cs.chromium.org/chromium/src/ios/chrome/browser/web/resources/accessibility.js). The problem is that interstitial page is created inside an individual WKWebView, thus doesn't have all the TabHelpers. If we want to use the same method in FontSizeTabHelper, we might need to call Javascript directly in CRWWebInterstitialImplWKWebViewDelegate.

eugenebut@ WDYT?

Proposal in comment #8 SGTM

BTW, I noticed that we also have an error page when the website or network is unavailable, which looks like the SSL warning page. It's not using ios/web/interstitials, and FontSizeTabHelper doesn't work for it either.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9ed979143a985a6753912a669cacd72e6a48956a

commit 9ed979143a985a6753912a669cacd72e6a48956a
Author: Yi Su <mrsuyi@chromium.org>
Date: Fri Jan 18 12:12:37 2019

Enable accessibility font size for interstitial page.

Currently interstitial page doesn't scale up web text when user uses
accessibility font size. FontSizeTabHelper doesn't work because
interstitial page is shown in another WebView of WebState. This CL uses
the same method from FontSizeTabHelper to enable accessibility font size
for interstitial page.

Bug:  891296 
Change-Id: Icea3a681e1861f419acbe12f7fbea5b044cf7e35
Reviewed-on: https://chromium-review.googlesource.com/c/1402809
Commit-Queue: Yi Su <mrsuyi@chromium.org>
Reviewed-by: Carlos IL <carlosil@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624081}
[modify] https://crrev.com/9ed979143a985a6753912a669cacd72e6a48956a/components/security_interstitials/core/browser/resources/interstitial_large.html
[modify] https://crrev.com/9ed979143a985a6753912a669cacd72e6a48956a/ios/chrome/browser/interstitials/BUILD.gn
[modify] https://crrev.com/9ed979143a985a6753912a669cacd72e6a48956a/ios/chrome/browser/interstitials/ios_security_interstitial_page.mm

Verified in 
Build: 73.0.3680.0 Canary
Device Details: iPhone XS Max(iOS 12.1.2), iPhone 8(iOS 11.4.1), iPad 2018(iOS 11.4.1)

Interstitial text is now scaling up as per the dynamic font size.