GitLab

Expose <webview>.contextMenus.onShow
chrome EventTarget like object so one can "addListener" that can
preventDefault() to cancel bringing up <webview> context menu.

BUG=465733
Test=Open a chrome app with <webview>. E.g.
Load a <webview> in a chrome app, e.g.
the browser sample app:
https://github.com/GoogleChrome/chrome-app-samples/tree/master/samples/webview-samples/browser

Right click on the <webview>, context menu is expected to be shown.

Now open the app's inspector: from chrome://inspect, switch to "Apps" then select to inspect "Browser sample".

Register a listener to disable context menu:

document.querySelector('webview').contextMenus.onShow.addListener(function(e) {
  e.preventDefault();
});

Right click on the <webview> again, context menu should not show up.

Review URL: https://codereview.chromium.org/1026383003

Cr-Commit-Position: refs/heads/master@{#322477}