Reland "[PiP v2] EnterPictureInPicture should return result"

This is a reland of 05df70856d90ad4560c2f39c2c35f297c0f5a4d1

Original change's description:
> [PiP v2] EnterPictureInPicture should return result
>
> Instead of returning the window size from EnterPictureInPicture
> we return a result enum as to whether the request was successful.
>
> We don't need to return the window size because we already have
> that in content.
>
> BUG=953957
>
> Change-Id: I982433de29f1ef4f13f4db24fdefd5f4f5e86d32
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1623464
> Reviewed-by: Avi Drissman <[email protected]>
> Reviewed-by: Jochen Eisinger <[email protected]>
> Reviewed-by: Mounir Lamouri <[email protected]>
> Commit-Queue: Becca Hughes <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#666760}

Bug: 953957
Change-Id: I02648d139b474ed6ef43cb06bf63fb9903f6cdca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1649188
Reviewed-by: Jochen Eisinger <[email protected]>
Reviewed-by: Mounir Lamouri <[email protected]>
Commit-Queue: Becca Hughes <[email protected]>
Cr-Commit-Position: refs/heads/master@{#668028}
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 7b97736b..62e3998 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -6800,12 +6800,12 @@
     outermost->SetAsFocusedWebContentsIfNecessary();
 }
 
-gfx::Size WebContentsImpl::EnterPictureInPicture(
+PictureInPictureResult WebContentsImpl::EnterPictureInPicture(
     const viz::SurfaceId& surface_id,
     const gfx::Size& natural_size) {
   return delegate_
              ? delegate_->EnterPictureInPicture(this, surface_id, natural_size)
-             : gfx::Size();
+             : PictureInPictureResult::kNotSupported;
 }
 
 void WebContentsImpl::ExitPictureInPicture() {