feat: emit devtools-open-url event for DevTools link selection

[codebytere]

Description of Change

Closes #36715.

This PR adds a new event devtools-open-url corresponding to a link in DevTools being either clicked or selected for opening in a new tab via context menu. There is precedent for event emission corresponding to DevToolsEmbedderMessageDispatcher::Delegate methods - this was previously a no-op and so the primary change here is adding an implementation to surface the action to developers.

Alternatively, we could potentially have implemented the new window behavior ourselves, but this is (imo) a large security hole and as such I believe we should ibstead give developers more fine-grained control over handling and optionally opening new links there.

Tested by adding:

mainWindow.loadURL('https://www.baidu.com/')

mainWindow.webContents.openDevTools()

mainWindow.webContents.on('devtools-open-url', (event, url) => {
  console.log(url)
})

to the createWindow method in a default Fiddle and confirming that url is correctly logged.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• relevant documentation, tutorials, templates and examples are changed or added
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Added a new devtools-open-url event to webContents to allow developers to open new windows with them.

[nornagon]

Chrome directs this through Browser::OpenURL: https://source.chromium.org/chromium/chromium/src/+/main:chrome/browser/devtools/devtools_ui_bindings.cc;l=196-201;drc=fd7b4c1844e6431a5ba4475eb515257a3a238a31

We have an open-url event on app already, but it seems to be only used on macOS, for when a user opens an app-registered URL. Oh well.

Let's call this devtools-open-url instead of devtools-open-in-new-tab.

[deepak1556]

Can we not just open the platform specific application to handle the URL

electron/shell/common/platform_util.h

Lines 33 to 37 in 20cff64

	// Open the given external protocol URL in the desktop's default manner.
	// (For example, mailto: URLs in the default mail user agent.)
	void OpenExternal(const GURL& url,
	const OpenExternalOptions& options,
	OpenCallback callback);

? Is it necessary for applications to handle this event ?

[codebytere]

@deepak1556 i considered that, but i think that allowing developers to decide for themselves is comparatively little effort and allows them to make a wider range of choices. I think it's reasonable for example to assume that a developer might want to open a URL in a new BrowserWindow within their own app, instead of shelling out to their external browser.

[jkleinsc]

API LGTM

[nornagon]

API LGTM

[ckerr]

API LGTM

[zcbenz]

API LGTM

[release-clerk]

Release Notes Persisted

Added a new devtools-open-url event to webContents to allow developers to open new windows with them.