[DevTools] Supply location instead of event to InspectorFrontendHost.showContextMenu method.

This change allows to show asynchronous menus.

BUG=none

Review URL: https://codereview.chromium.org/362253003

git-svn-id: svn://svn.chromium.org/blink/trunk@177537 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Preload HTML documents content before fetching resource content.

This is a last step in fixing the issue of HTML document content being unavailable when DevTools is first opened.
This patch adds HTML document content fetching logic as well as fixing all the tests that somehow depend on it.

BUG=354447

Review URL: https://codereview.chromium.org/337783003

git-svn-id: svn://svn.chromium.org/blink/trunk@177538 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make access-control-basic-get-fail-non-simple.cgi output 403 for OPTIONS explicitly

BUG=391391

Review URL: https://codereview.chromium.org/368353003

git-svn-id: svn://svn.chromium.org/blink/trunk@177539 bbb929c8-8fbe-4397-9dbb-9b2b20218538