[COOP] access reporting: Clear old CoopAccessMonitor.

Clear CoopAccessMonitor when their reporter are gone. This avoids
accumulating them.
Similarly, because we don't have RenderDocument, the accessing
LocalFrame might host new documents. A new CoopAccessMonitor will be
sent after the commit. The new one must
replace the old one. This will allow the new set or reported URLs to be
reported.

This is a positive change, but still not perfect at all. Ideally, the
CoopAccessMonitor(s) passed into process of the new Document should be
passed along the CommitNavigation IPC.

Bug: 1090273
Change-Id: Ib444e760175207702867f47012fa05bd5e051576
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2408752Reviewed-by: Camille Lamy <clamy@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806625}

third_party/blink/renderer/core/frame/dom_window.cc

@@ -446,10 +446,27 @@ void DOMWindow::InstallCoopAccessMonitor(
   monitor.report_type = report_type;
   monitor.accessing_main_frame = accessing_frame->GetFrameToken();
 
-  // TODO(arthursonzogni): Clean coop_access_monitor_ when a reporter is gone.
-  // Use mojo::Remote::set_disconnect_handler.
   monitor.reporter.Bind(std::move(pending_reporter));
-
+  // CoopAccessMonitor are cleared when their reporter are gone. This avoids
+  // accumulation. However it would have been interesting continuing reporting
+  // accesses past this point, at least for the ReportingObserver and Devtool.
+  // TODO(arthursonzogni): Consider observing |accessing_main_frame| deletion
+  // instead.
+  monitor.reporter.set_disconnect_handler(
+      WTF::Bind(&DOMWindow::DisconnectCoopAccessMonitor,
+                WrapWeakPersistent(this), monitor.accessing_main_frame));
+
+  // As long as RenderDocument isn't shipped, it can exist a CoopAccessMonitor
+  // for the same |accessing_main_frame|, because it might now host a different
+  // Document. Same is true for |this| DOMWindow, it might refer to a window
+  // hosting a different document.
+  // The new documents will still be part of a different virtual browsing
+  // context group, however the new COOPAccessMonitor might now contain updated
+  // URLs.
+  DisconnectCoopAccessMonitor(monitor.accessing_main_frame);
+
+  // Any attempts to access |this| window from |accessing_main_frame| will now
+  // trigger reports (network, ReportingObserver, Devtool).
   coop_access_monitor_.push_back(std::move(monitor));
 }
 
@@ -632,4 +649,15 @@ void DOMWindow::Trace(Visitor* visitor) const {
   EventTargetWithInlineData::Trace(visitor);
 }
 
+void DOMWindow::DisconnectCoopAccessMonitor(
+    base::UnguessableToken accessing_main_frame) {
+  auto* it = coop_access_monitor_.begin();
+  while (it != coop_access_monitor_.end()) {
+    if (it->accessing_main_frame == accessing_main_frame)
+      it = coop_access_monitor_.erase(it);
+    else
+      ++it;
+  }
+}
+
 }  // namespace blink

third_party/blink/renderer/core/frame/dom_window.h

@@ -165,6 +165,11 @@ class CORE_EXPORT DOMWindow : public EventTargetWithInlineData {
                      LocalDOMWindow* source,
                      ExceptionState&);
 
+  // Removed the CoopAccessMonitor with the given |accessing_main_frame| from
+  // the |coop_access_monitor| list. This is called when the COOP reporter is
+  // gone or a more recent CoopAccessMonitor is being added.
+  void DisconnectCoopAccessMonitor(base::UnguessableToken accessing_main_frame);
+
   Member<Frame> frame_;
   // Unlike |frame_|, |window_proxy_manager_| is available even after the
   // window's frame gets detached from the DOM, until the end of the lifetime