Bug 1689601, sync fields when loading a page from bfcache, r=peterv

Differential Revision: https://phabricator.services.mozilla.com/D106737

docshell/base/CanonicalBrowsingContext.cpp

@@ -168,14 +168,24 @@ void CanonicalBrowsingContext::ReplacedBy(
     mStatusFilter = nullptr;
   }
   aNewContext->mWebProgress = std::move(mWebProgress);
-  aNewContext->mFields.SetWithoutSyncing<IDX_BrowserId>(GetBrowserId());
-  aNewContext->mFields.SetWithoutSyncing<IDX_HistoryID>(GetHistoryID());
-  aNewContext->mFields.SetWithoutSyncing<IDX_ExplicitActive>(
-      GetExplicitActive());
+
+  // Use the Transaction for the fields which need to be updated whether or not
+  // the new context has been attached before.
+  // SetWithoutSyncing can be used if context hasn't been attached.
+  Transaction txn;
+  txn.SetBrowserId(GetBrowserId());
+  txn.SetHistoryID(GetHistoryID());
+  txn.SetExplicitActive(GetExplicitActive());
+  if (aNewContext->EverAttached()) {
+    MOZ_ALWAYS_SUCCEEDS(txn.Commit(aNewContext));
+  } else {
+    txn.CommitWithoutSyncing(aNewContext);
+  }
 
   // XXXBFCache name handling is still a bit broken in Fission in general,
   // at least in case name should be cleared.
   if (aRemotenessOptions.mTryUseBFCache) {
+    MOZ_ASSERT(!aNewContext->EverAttached());
     aNewContext->mFields.SetWithoutSyncing<IDX_Name>(GetName());
     aNewContext->mFields.SetWithoutSyncing<IDX_HasLoadedNonInitialDocument>(
         GetHasLoadedNonInitialDocument());

docshell/base/SyncedContext.h

@@ -74,6 +74,16 @@ class Transaction {
   mozilla::ipc::IPCResult CommitFromIPC(const MaybeDiscarded<Context>& aOwner,
                                         uint64_t aEpoch, ContentChild* aSource);
 
+  // Apply the changes from this transaction to the specified Context WITHOUT
+  // syncing the changes to other processes.
+  //
+  // Unlike `Commit`, this method will NOT call the corresponding `CanSet` or
+  // `DidSet` methods, and can be performed when the target context is
+  // unattached or discarded.
+  //
+  // NOTE: YOU PROBABLY DO NOT WANT TO USE THIS METHOD
+  void CommitWithoutSyncing(Context* aOwner);
+
  private:
   friend struct mozilla::ipc::IPDLParamTraits<Transaction<Context>>;
 

docshell/base/SyncedContextInlines.h

@@ -223,6 +223,22 @@ void Transaction<Context>::Apply(Context* aOwner, bool aFromIPC) {
   mModified.clear();
 }
 
+template <typename Context>
+void Transaction<Context>::CommitWithoutSyncing(Context* aOwner) {
+  MOZ_LOG(
+      Context::GetSyncLog(), LogLevel::Debug,
+      ("Transaction::CommitWithoutSyncing(#%" PRIx64 "): %s", aOwner->Id(),
+       FormatTransaction<Context>(mModified, aOwner->mFields.mValues, mValues)
+           .get()));
+
+  EachIndex([&](auto idx) {
+    if (mModified.contains(idx)) {
+      aOwner->mFields.mValues.Get(idx) = std::move(mValues.Get(idx));
+    }
+  });
+  mModified.clear();
+}
+
 inline CanSetResult AsCanSetResult(CanSetResult aValue) { return aValue; }
 inline CanSetResult AsCanSetResult(bool aValue) {
   return aValue ? CanSetResult::Allow : CanSetResult::Deny;