Implement RequestToLockMouse in HeadlessWebContentsImpl::Delegate

There are a few wpt pointerlock tests that fail under the new wpt try
bots.

The wpt try bots are running wpt run in headless mode.
Turns out that, when running wpt tests in headless mode with the wpt
runner,the code is reaching this line in
WebContentsImpl::RequestToLockMouse [1].
The problem here is that delegate_->RequestToLockMouse is actually
the empty implementation from WebContentsDelegate::RequestToLockMouse.
This is why the WebContents::GotResponseToLockMouseRequest is never
called.
The expectation for WebContentsDelegate::RequestToLockMouse is to call
WebContents::GotResponseToLockMouseRequest like other code paths.

The culprit is HeadlessWebContentsImpl:Delegate, which inherits the
empty implementation of WebContentsDelegate::RequestToLockMouse.

When running the wpt tests without --headless the delegate is an
instance of Browser class.

Implement HeadlessWebContentsImpl:Delegate::RequestToLockMouse similar
to what we do for content shell.

[1] https://www.google.com/url?q=https://source.chromium.org/chromium/chromium/src/%2B/master:content/browser/web_contents/web_contents_impl.cc;drc%3D3fab4813ccc76de821bb74b441ff491afc8a7a6f;l%3D3402&sa=D&source=calendar&ust=1608479687279000&usg=AOvVaw2Q3jZFrFsbSnQd8osPwpOU

TEST=external/wpt/pointerevents/pointerlock/pointerevent_getCoalescedEvents_when_pointerlocked.html,external/wpt/pointerevents/pointerlock/pointerevent_coordinates_when_locked.html,external/wpt/pointerevents/pointerlock/pointerevent_getCoalescedEvents_when_pointerlocked.html,external/wpt/pointerevents/pointerlock/pointerevent_movementxy_with_pointerlock.html,external/wpt/pointerevents/pointerlock/pointerevent_pointerlock_after_pointercapture.html,external/wpt/pointerevents/pointerlock/pointerevent_pointermove_in_pointerlock.html,external/wpt/pointerevents/pointerlock/pointerevent_pointermove_on_chorded_mouse_button_when_locked.html

Bug: 1127055
Change-Id: Ic1da165fed1dc1902c5e8c0dbb5f7cfc7513ee30
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2594009Reviewed-by: Mustaq Ahmed <mustaq@chromium.org>
Reviewed-by: Peter Kvitek <kvitekp@chromium.org>
Commit-Queue: Liviu Tinta <liviutinta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841490}

headless/lib/browser/headless_web_contents_impl.cc

@@ -177,6 +177,13 @@ class HeadlessWebContentsImpl::Delegate : public content::WebContentsDelegate {
         ->block_new_web_contents();
   }
 
+  void RequestToLockMouse(content::WebContents* web_contents,
+                          bool user_gesture,
+                          bool last_unlocked_by_target) override {
+    web_contents->GotResponseToLockMouseRequest(
+        blink::mojom::PointerLockResult::kSuccess);
+  }
+
  private:
   HeadlessBrowserImpl* browser() { return headless_web_contents_->browser(); }
 

third_party/blink/web_tests/external/wpt/pointerevents/pointerlock/pointerevent_coordinates_when_locked.html.ini

-[pointerevent_coordinates_when_locked.html]
-  expected: TIMEOUT
-
-  [mouse Test pointerevent coordinates when pointer is locked]
-    expected: NOTRUN

third_party/blink/web_tests/external/wpt/pointerevents/pointerlock/pointerevent_getCoalescedEvents_when_pointerlocked.html.ini

-[pointerevent_getCoalescedEvents_when_pointerlocked.html]
-  [mouse pointermove getCoalescedEvents when lock test]
-    expected: FAIL

third_party/blink/web_tests/external/wpt/pointerevents/pointerlock/pointerevent_movementxy_with_pointerlock.html.ini

-[pointerevent_movementxy_with_pointerlock.html]
-  expected: TIMEOUT
-
-  [mouse pointerevent movementX/Y with pointerlock test]
-    expected: TIMEOUT
-    message: Test timed out

third_party/blink/web_tests/external/wpt/pointerevents/pointerlock/pointerevent_pointerlock_after_pointercapture.html.ini

-[pointerevent_pointerlock_after_pointercapture.html]
-  [mouse no pointercapture while pointerlock]
-    expected: FAIL

third_party/blink/web_tests/external/wpt/pointerevents/pointerlock/pointerevent_pointermove_in_pointerlock.html.ini

-[pointerevent_pointermove_in_pointerlock.html]
-  expected: TIMEOUT
-
-  [pointermove event received]
-    expected: NOTRUN
-
-  [pointermove event received inner frame]
-    expected: NOTRUN

third_party/blink/web_tests/external/wpt/pointerevents/pointerlock/pointerevent_pointermove_on_chorded_mouse_button_when_locked.html.ini

-[pointerevent_pointermove_on_chorded_mouse_button_when_locked.html]
-  expected: TIMEOUT
-
-  [pointer locked pointermove events received for button state changes]
-    expected: NOTRUN