Bug 1545474 - Part 3: Test eviction of content viewer entries, r=peterv

Add a new callback to session history listener to listen for content
viewers being evicted.

Differential Revision: https://phabricator.services.mozilla.com/D32731

--HG--
extra : rebase_source : 29c8e9299af718e75029dfae4e937a3d4f18900d
extra : amend_source : 19e679c6d2721dd7e8d7da1ec7af3033439210b4
extra : source : 5e4d0ab9e52ce1e1d1684fdb59534a66e9f9d9b9
extra : histedit_source : 44e9cb7ba0589c79c03b2dc58ec4d0d4c0c98422

docshell/shistory/PSHistory.ipdl

@@ -58,7 +58,7 @@ parent:
   sync Evict(PSHEntry[] entry);
   sync EnsureCorrectEntryAtCurrIndex(PSHEntry entry);
   sync EvictContentViewersOrReplaceEntry(nullable PSHEntry newSHEntry, bool replace);
-
+  async NotifyListenersContentViewerEvicted(uint32_t numEvicted);
   async __delete__();
 };
 

docshell/shistory/SHEntryChild.cpp

@@ -53,16 +53,25 @@ void SHEntryChildShared::EvictContentViewers(
   MOZ_ASSERT(sSHEntryChildSharedTable,
              "we have content viewers to evict, but the table hasn't been "
              "initialized yet");
+  uint32_t numEvictedSoFar = 0;
   for (auto iter = aToEvictSharedStateIDs.begin();
        iter != aToEvictSharedStateIDs.end(); ++iter) {
     RefPtr<SHEntryChildShared> shared = sSHEntryChildSharedTable->Get(*iter);
     MOZ_ASSERT(shared, "shared entry can't be null");
     nsCOMPtr<nsIContentViewer> viewer = shared->mContentViewer;
     if (viewer) {
+      numEvictedSoFar++;
       shared->SetContentViewer(nullptr);
       shared->SyncPresentationState();
       viewer->Destroy();
     }
+    if (std::next(iter) == aToEvictSharedStateIDs.end() &&
+        numEvictedSoFar > 0) {
+      // This is the last shared object, so we should notify our
+      // listeners about any content viewers that were evicted.
+      // It does not matter which shared entry we will use for notifying.
+      shared->NotifyListenersContentViewerEvicted(numEvictedSoFar);
+    }
   }
 }
 
@@ -134,6 +143,13 @@ void SHEntryChildShared::DropPresentationState() {
   mEditorData = nullptr;
 }
 
+void SHEntryChildShared::NotifyListenersContentViewerEvicted(
+    uint32_t aNumEvicted) {
+  if (StaticPrefs::docshell_shistory_testing_bfevict() && mSHistory) {
+    mSHistory->SendNotifyListenersContentViewerEvicted(aNumEvicted);
+  }
+}
+
 nsresult SHEntryChildShared::SetContentViewer(nsIContentViewer* aViewer) {
   MOZ_ASSERT(!aViewer || !mContentViewer,
              "SHEntryShared already contains viewer");
@@ -994,6 +1010,7 @@ void SHEntryChild::EvictContentViewer() {
   if (viewer) {
     // Drop the presentation state before destroying the viewer, so that
     // document teardown is able to correctly persist the state.
+    mShared->NotifyListenersContentViewerEvicted();
     SetContentViewer(nullptr);
     SyncPresentationState();
     viewer->Destroy();

docshell/shistory/SHEntryChild.h

@@ -45,6 +45,8 @@ class SHEntryChildShared final : public nsIBFCacheEntry,
   static void EvictContentViewers(
       const nsTArray<uint64_t>& aToEvictSharedStateIDs);
 
+  void NotifyListenersContentViewerEvicted(uint32_t aNumEvicted = 1);
+
   NS_DECL_ISUPPORTS
   NS_DECL_NSIBFCACHEENTRY
 

docshell/shistory/SHistoryParent.cpp

@@ -239,6 +239,12 @@ bool SHistoryParent::RecvEvict(nsTArray<PSHEntryParent*>&& aEntries) {
   return true;
 }
 
+bool SHistoryParent::RecvNotifyListenersContentViewerEvicted(
+    uint32_t aNumEvicted) {
+  mHistory->NotifyListenersContentViewerEvicted(aNumEvicted);
+  return true;
+}
+
 void LegacySHistory::EvictOutOfRangeWindowContentViewers(int32_t aIndex) {
   if (aIndex < 0) {
     return;

docshell/shistory/SHistoryParent.h

@@ -80,6 +80,7 @@ class SHistoryParent final : public PSHistoryParent {
   bool RecvEvict(nsTArray<PSHEntryParent*>&& aEntries);
   bool RecvEnsureCorrectEntryAtCurrIndex(PSHEntryParent* aEntry);
   bool RecvEvictContentViewersOrReplaceEntry(PSHEntryParent* aNewSHEntry, bool aReplace);
+  bool RecvNotifyListenersContentViewerEvicted(uint32_t aNumEvicted);
 
   RefPtr<CanonicalBrowsingContext> mContext;
   RefPtr<LegacySHistory> mHistory;

docshell/shistory/nsISHistoryListener.idl

@@ -65,4 +65,14 @@ interface nsISHistoryListener : nsISupports
    * about pages) and when history.replaceState is called.
    */
   void OnHistoryReplaceEntry();
+
+
+  /**
+   * Called whenever a content viewer is evicted. A content viewer is evicted
+   * whenever a bfcache entry has timed out or the number of total content
+   * viewers has exceeded the global max. This is used for testing only.
+   *
+   * @param aNumEvicted - number of content viewers evicted
+   */
+  void OnContentViewerEvicted(in unsigned long aNumEvicted);
 };

docshell/shistory/nsSHEntry.cpp

@@ -1038,6 +1038,7 @@ nsLegacySHEntry::CreateLoadInfo(nsDocShellLoadState** aLoadState) {
 void nsSHEntry::EvictContentViewer() {
   nsCOMPtr<nsIContentViewer> viewer = GetContentViewer();
   if (viewer) {
+    mShared->NotifyListenersContentViewerEvicted();
     // Drop the presentation state before destroying the viewer, so that
     // document teardown is able to correctly persist the state.
     SetContentViewer(nullptr);

docshell/shistory/nsSHEntryShared.cpp

@@ -52,6 +52,13 @@ void dom::SHEntrySharedParentState::CopyFrom(
   mLastTouched = aEntry->mLastTouched;
 }
 
+void dom::SHEntrySharedParentState::NotifyListenersContentViewerEvicted() {
+  if (nsCOMPtr<nsISHistory> shistory = do_QueryReferent(mSHistory)) {
+    RefPtr<nsSHistory> nsshistory = static_cast<nsSHistory*>(shistory.get());
+    nsshistory->NotifyListenersContentViewerEvicted(1);
+  }
+}
+
 dom::SHEntrySharedChildState::SHEntrySharedChildState()
     : mSaveLayoutState(true) {}
 

docshell/shistory/nsSHEntryShared.h

@@ -51,6 +51,8 @@ class SHEntrySharedParentState {
 
   uint64_t GetID() const { return mID; }
 
+  void NotifyListenersContentViewerEvicted();
+
  protected:
   friend class nsSHEntry;
 

docshell/shistory/nsSHistory.cpp

@@ -179,6 +179,7 @@ void nsSHistory::EvictContentViewerForEntry(nsISHEntry* aEntry) {
 
     // Drop the presentation state before destroying the viewer, so that
     // document teardown is able to correctly persist the state.
+    NotifyListenersContentViewerEvicted(1);
     aEntry->SetContentViewer(nullptr);
     aEntry->SyncPresentationState();
     viewer->Destroy();
@@ -745,6 +746,10 @@ nsSHistory::AddSHistoryListener(nsISHistoryListener* aListener) {
   return NS_OK;
 }
 
+void nsSHistory::NotifyListenersContentViewerEvicted(uint32_t aNumEvicted) {
+  NOTIFY_LISTENERS(OnContentViewerEvicted, (aNumEvicted));
+}
+
 NS_IMETHODIMP
 nsSHistory::RemoveSHistoryListener(nsISHistoryListener* aListener) {
   // Make sure the listener that wants to be removed is the

docshell/shistory/nsSHistory.h

@@ -143,6 +143,7 @@ class nsSHistory : public mozilla::LinkedListElement<nsSHistory>,
 
   void WindowIndices(int32_t aIndex, int32_t* aOutStartIndex,
                      int32_t* aOutEndIndex);
+  void NotifyListenersContentViewerEvicted(uint32_t aNumEvicted);
 
  protected:
   virtual ~nsSHistory();

docshell/test/navigation/browser.ini

@@ -7,6 +7,7 @@ support-files =
   bug343515_pg3_1_1.html
   bug343515_pg3_2.html
 
+[browser_test_bfcache_eviction.js]
 [browser_bug343515.js]
 [browser_test-content-chromeflags.js]
 tags = openwindow

docshell/test/navigation/browser_test_bfcache_eviction.js

@@ -0,0 +1,63 @@
+add_task(async function() {
+  // We don't want the number of total viewers to be calculated by the available size
+  // for this test case. Instead, fix the number of viewers.
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.sessionhistory.max_total_viewers", 3],
+      ["docshell.shistory.testing.bfevict", true],
+    ],
+  });
+
+  // 1. Open a tab
+  var testPage =
+    "data:text/html,<html id='html1'><body id='body1'></body></html>";
+  await BrowserTestUtils.withNewTab({ gBrowser, url: testPage }, async function(
+    browser
+  ) {
+    // 2.  Add a promise that will be resolved when the 'content viewer evicted' event goes off
+    let testDone = {};
+    testDone.promise = new Promise(resolve => {
+      testDone.resolve = resolve;
+    });
+
+    let legacySHistory = browser.browsingContext.sessionHistory;
+    // 3. Register a session history listener to listen for a 'content viewer evicted' event.
+    let historyListener = {
+      OnContentViewerEvicted() {
+        ok(
+          true,
+          "History listener got called after a content viewer was evicted"
+        );
+        legacySHistory.removeSHistoryListener(historyListener);
+        // 6. Resolve the promise when we got our 'content viewer evicted' event
+        testDone.resolve();
+      },
+      QueryInterface: ChromeUtils.generateQI([
+        Ci.nsISHistoryListener,
+        Ci.nsISupportsWeakReference,
+      ]),
+    };
+    legacySHistory.addSHistoryListener(historyListener);
+
+    // 4. Open a second tab
+    testPage = `data:text/html,<html id='html1'><body id='body1'>I am a second tab!</body></html>`;
+    let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, testPage);
+
+    // 5. Navigate the first tab to 4 different pages.
+    // We should get 1 content viewer evicted because it will be outside of the range.
+    // If we have the following pages in our session history: P1 P2 P3 P4 P5
+    // and we are currently at P5, then P1 is outside of the range
+    // (it is more than 3 entries away from current entry) and thus will be evicted.
+    for (var i = 0; i < 4; i++) {
+      testPage = `data:text/html,<html id='html1'><body id='body1'>${i}</body></html>`;
+      let pagePromise = BrowserTestUtils.browserLoaded(browser);
+      await BrowserTestUtils.loadURI(browser, testPage);
+      await pagePromise;
+    }
+    // 7. Wait for 'content viewer evicted' event to go off
+    await testDone.promise;
+
+    // 8. Close the second tab
+    BrowserTestUtils.removeTab(tab2);
+  });
+});

modules/libpref/init/StaticPrefList.yaml

@@ -1234,6 +1234,17 @@
   value: true
   mirror: always
 
+#---------------------------------------------------------------------------
+# Prefs starting with "docshell."
+#---------------------------------------------------------------------------
+
+# Used to indicate whether session history listeners should be notified
+# about content viewer eviction. Used only for testing.
+- name: docshell.shistory.testing.bfevict
+  type: bool
+  value: false
+  mirror: always
+
 #---------------------------------------------------------------------------
 # Prefs starting with "dom."
 #---------------------------------------------------------------------------

modules/libpref/moz.build

@@ -36,6 +36,7 @@ pref_groups = [
     'content',
     'device',
     'devtools',
+    'docshell',
     'dom',
     'editor',
     'extensions',