Google Chrome removed the flag that offered the ability to save a web page and sub-resources in it as a single text file. “Save Page as MHTML flag” available in Google Chrome since 2012 to till now, has been removed in latest Chrome Canary, however, still you can save a page as a single file in Chrome without that flag.
Save Page as MHTML flag removed
Recently Chromium-based Vivaldi offered Save Page as HTML feature by default in version 2.3 without needing to enable flag, so if you’re using Vivaldi you don’t need to worry.
If you’ve enabled the feature in about:flags and using it in Chrome you’ll notice it stop working one day in a future version of Chrome where if you right click on a page and select “save as”, Webpage, Single file type doesn’t appear in Save as dialog.

Fret not! you can still continue to store pages as single files using Chrome. you should be running the browser with this command line switch.
1. Right click on Chrome shortcut on the desktop
2. Select “Properties”
3. In the Target field after Chrome.exe give space and add --save-page-as-mhtml
4. Click Apply, give administrator permission by clicking Continue.
Now visit any website, right click and choose “save as”, click “Save as”, here by default Save as type will be set to “Web Page, single file”. You can open the MHTML files created this way in Internet Explorer.