[Security] Introduce the COOP member to RenderFrameHost.

A CL aimed at reducing dependencies of other concurrent CLs. Does
nothing in itself but introduce an unused cross_origin_opener_policy_
member to RenderFrameHostImpl.

Based on and grouped with COEP.

Bug: 922191
Change-Id: I5331da7ad287d56294029fbb2885b02799ed1d5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1963795
Commit-Queue: Arthur Hemery <ahemery@chromium.org>
Reviewed-by: Pâris Meuleman <pmeuleman@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#724554}

content/browser/frame_host/render_frame_host_impl.h

@@ -1221,6 +1221,16 @@ class CONTENT_EXPORT RenderFrameHostImpl
     cross_origin_embedder_policy_ = policy;
   }
 
+  // Semi-formal definition of COOP:
+  // https://gist.github.com/annevk/6f2dd8c79c77123f39797f6bdac43f3e
+  network::mojom::CrossOriginOpenerPolicy cross_origin_opener_policy() const {
+    return cross_origin_opener_policy_;
+  }
+  void set_cross_origin_opener_policy(
+      network::mojom::CrossOriginOpenerPolicy policy) {
+    cross_origin_opener_policy_ = policy;
+  }
+
   // This function mimics DidCommitProvisionalLoad for navigations served from
   // the back-forward cache.
   void DidCommitBackForwardCacheNavigation(
@@ -2035,6 +2045,9 @@ class CONTENT_EXPORT RenderFrameHostImpl
   network::mojom::CrossOriginEmbedderPolicy cross_origin_embedder_policy_ =
       network::mojom::CrossOriginEmbedderPolicy::kNone;
 
+  network::mojom::CrossOriginOpenerPolicy cross_origin_opener_policy_ =
+      network::mojom::CrossOriginOpenerPolicy::kUnsafeNone;
+
   // Track the site URL of the last site we committed successfully, as obtained
   // from SiteInstance::GetSiteURL.
   GURL last_committed_site_url_;