Bug 1663757 - Part 4: Track current remote URI on CanonicalBrowsingContext, r=annyG,farre

This URI is intended to reflect the currentURI field on the content nsIDocShell,
and is the value used for getters like `window.location.href`. For most
documents, this generally matches the Document URI on WindowGlobalParent, it
does not match in specific cases such as error pages or when performing a
session restore.

The field is kept up-to-date by listening to `OnLocationChange` notifications
from the content process, and is ignored when the BrowsingContext is loaded in
the parent process.

Differential Revision: https://phabricator.services.mozilla.com/D105559

docshell/base/CanonicalBrowsingContext.cpp

@@ -70,6 +70,10 @@ CanonicalBrowsingContext::CanonicalBrowsingContext(WindowContext* aParentWindow,
   // You are only ever allowed to create CanonicalBrowsingContexts in the
   // parent process.
   MOZ_RELEASE_ASSERT(XRE_IsParentProcess());
+
+  // The initial URI in a BrowsingContext is always "about:blank".
+  MOZ_ALWAYS_SUCCEEDS(
+      NS_NewURI(getter_AddRefs(mCurrentRemoteURI), "about:blank"));
 }
 
 /* static */
@@ -1656,6 +1660,22 @@ void CanonicalBrowsingContext::EndDocumentLoad(bool aForProcessSwitch) {
   }
 }
 
+already_AddRefed<nsIURI> CanonicalBrowsingContext::GetCurrentURI() const {
+  nsCOMPtr<nsIURI> currentURI;
+  if (nsIDocShell* docShell = GetDocShell()) {
+    MOZ_ALWAYS_SUCCEEDS(
+        nsDocShell::Cast(docShell)->GetCurrentURI(getter_AddRefs(currentURI)));
+  } else {
+    currentURI = mCurrentRemoteURI;
+  }
+  return currentURI.forget();
+}
+
+void CanonicalBrowsingContext::SetCurrentRemoteURI(nsIURI* aCurrentRemoteURI) {
+  MOZ_ASSERT(!GetDocShell());
+  mCurrentRemoteURI = aCurrentRemoteURI;
+}
+
 void CanonicalBrowsingContext::ResetSHEntryHasUserInteractionCache() {
   WindowContext* topWc = GetTopWindowContext();
   if (topWc && !topWc->IsDiscarded()) {

docshell/base/CanonicalBrowsingContext.h

@@ -208,6 +208,10 @@ class CanonicalBrowsingContext final : public BrowsingContext {
   void Reload(uint32_t aReloadFlags);
   void Stop(uint32_t aStopFlags);
 
+  // Get the publicly exposed current URI loaded in this BrowsingContext.
+  already_AddRefed<nsIURI> GetCurrentURI() const;
+  void SetCurrentRemoteURI(nsIURI* aCurrentRemoteURI);
+
   BrowserParent* GetBrowserParent() const;
 
   // Internal method to change which process a BrowsingContext is being loaded
@@ -360,6 +364,10 @@ class CanonicalBrowsingContext final : public BrowsingContext {
   // entries are added or replaced.
   void ResetSHEntryHasUserInteractionCache();
 
+  // The current URI loaded in this BrowsingContext. This value is only set for
+  // BrowsingContexts loaded in content processes.
+  nsCOMPtr<nsIURI> mCurrentRemoteURI;
+
   // The current remoteness change which is in a pending state.
   RefPtr<PendingRemotenessChange> mPendingRemotenessChange;
 

dom/chrome-webidl/BrowsingContext.webidl

@@ -3,6 +3,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+interface URI;
 interface nsIDocShell;
 interface nsISecureBrowserUI;
 interface nsIWebProgress;
@@ -265,6 +266,10 @@ interface CanonicalBrowsingContext : BrowsingContext {
   readonly attribute MediaController? mediaController;
 
   void resetScalingZoom();
+
+  // The current URI loaded in this BrowsingContext according to nsDocShell.
+  // This may not match the current window global's document URI in some cases.
+  readonly attribute URI? currentURI;
 };
 
 [Exposed=Window, ChromeOnly]

dom/ipc/BrowserParent.cpp

@@ -2686,6 +2686,8 @@ mozilla::ipc::IPCResult BrowserParent::RecvOnLocationChange(
     return IPC_OK();
   }
 
+  browsingContext->SetCurrentRemoteURI(aLocation);
+
   nsCOMPtr<nsIBrowser> browser = GetBrowser();
   if (!mozilla::SessionHistoryInParent() && browser) {
     Unused << browser->UpdateWebNavigationForLocationChange(aCanGoBack,