Implement NavigationThrottle::BLOCK_REQUEST_AND_COLLAPSE.

content/browser/frame_host/frame_tree_node.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_NODE_H_
 #define CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_NODE_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 119 matching lines @@
 
   // Sets the last committed URL for this frame and updates
   // has_committed_real_load accordingly.
   void SetCurrentURL(const GURL& url);
 
   // Returns true iff SetCurrentURL has been called with a non-blank URL.
   bool has_committed_real_load() const {
     return has_committed_real_load_;
   }
 
+  // Returns whether the frame's owner element in the parent frame is collapsed
+  // as per request by the client, i.e. it should not appear in the layout.
+  bool is_frame_owner_collapsed() const { return is_frame_owner_collapsed_; }
+
+  // Sets whether to collapse, i.e. exclude from the layout, the frame's owner
+  // element in the parent frame. Not applicable to main frames, and will have
+  // no effect unless the child frame is embedded using an <iframe> element.
+  void SetFrameOwnerCollapsedState(bool collapsed);
+
   // Returns the origin of the last committed page in this frame.
   // WARNING: To get the last committed origin for a particular
   // RenderFrameHost, use RenderFrameHost::GetLastCommittedOrigin() instead,
   // which will behave correctly even when the RenderFrameHost is not the
   // current one for this frame (such as when it's pending deletion).
   const url::Origin& current_origin() const {
     return replication_state_.origin;
   }
 
   // Set the current origin and notify proxies about the update.
@@ skipping 189 matching lines @@
   // is disowned.
   std::unique_ptr<OpenerDestroyedObserver> opener_observer_;
 
   // The immediate children of this specific frame.
   std::vector<std::unique_ptr<FrameTreeNode>> children_;
 
   // Whether this frame has committed any real load, replacing its initial
   // about:blank page.
   bool has_committed_real_load_;
 
+  // Whether the frame's owner element in the parent frame is collapsed, i.e. it
+  // does not appear in the layout. Always false for main frames, and has have
+  // no effect unless the child frame is embedded using an <iframe> element.
+  bool is_frame_owner_collapsed_;

[nasko, 2017/01/19 00:11:46]

Why does the browser process need to know this?

[engedy, 2017/02/17 18:09:25]

As discussed offline, this is required to avoid needing to send `uncollapse`
IPCs on every allowed navigation.

Storing it on FrameOwnerProperties is not an option either, because the current
unidirectional FOP propagation logic requires the HTMLIFrameElement to update
it, but with this round trip we no longer have strong enough consistency
guarantees to reliably tell on the browser side if the `collapsed` actually
changed (and avoid sending IPCs if it didn't).

I now believe this lack of consistency actually rules out renderer-side
solutions too if we want to optimize sending IPCs based on whether there was an
actual `collapsed` state transition; because the update lag affects the copy on
RemoteFrameOwner too.

+
   // Track information that needs to be replicated to processes that have
   // proxies for this frame.
   FrameReplicationState replication_state_;
 
   // Track the pending sandbox flags for this frame.  When a parent frame
   // dynamically updates sandbox flags in the <iframe> element for a child
   // frame, these updated flags are stored here and are transferred into
   // replication_state_.sandbox_flags when they take effect on the next frame
   // navigation.
   blink::WebSandboxFlags pending_sandbox_flags_;
@@ skipping 23 matching lines @@
   // browser process activities to this node (when possible).  It is unrelated
   // to the core logic of FrameTreeNode.
   FrameTreeNodeBlameContext blame_context_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameTreeNode);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_NODE_H_