Version: M53 Beta - 53.0.2785.80
OS: OSX, likely others.

What steps will reproduce the problem?
(1) Open chrome://cast page. Notice the <extensionview> element with an embedded "chrome-extension://enhhojjnijigcajfphajepfemndkmdlo/cast_setup/index.html#devices" page.

(2) Inspect the extension page: be sure to got through chrome://inspect/#pages. Select the chrome-extension:// page listed under the chrome://cast/#devices page.

(3) In the JS console of the extension page, run the following code:
chrome.extension.getViews().map(view => view.window.location.href)

What is the expected output?
["chrome-extension://enhhojjnijigcajfphajepfemndkmdlo/cast_setup/index.html#devices", "chrome-extension://enhhojjnijigcajfphajepfemndkmdlo/_generated_background_page.html"]

What do you see instead?
["chrome-extension://enhhojjnijigcajfphajepfemndkmdlo/_generated_background_page.html"]


Some notes:

(1) This works correctly when "chrome-extension://enhhojjnijigcajfphajepfemndkmdlo/cast_setup/index.html#devices" is opened in its own tab, instead of the inside the extensionview.

(2) The page inside the <extensionview> is not completely cut off from the rest of the extension: chrome.runtime.sendMessage works for communicating with the event page.
 

Deleted: Screen Shot 2016-08-31 at 8.04.46 AM.png 65.9 KB

	Screen Shot 2016-08-31 at 8.04.46 AM.png 65.9 KB View Download