--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -1243,17 +1243,18 @@ BrowserGlue.prototype = {
           DefaultBrowserCheck.prompt(RecentWindow.getMostRecentBrowserWindow());
         }.bind(this), Ci.nsIThread.DISPATCH_NORMAL);
       }
     }
 
     if (AppConstants.E10S_TESTING_ONLY) {
       E10SUINotification.checkStatus();
     }
-    if (AppConstants.platform == "win") {
+    if (AppConstants.platform == "win" ||
+        AppConstants.platform == "macosx") {
       // Handles prompting to inform about incompatibilites when accessibility
       // and e10s are active together.
       E10SAccessibilityCheck.init();
     }
   },
 
   _createExtraDefaultProfile: function () {
     if (!AppConstants.MOZ_DEV_EDITION) {

--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -4658,31 +4658,31 @@ enum {
   // kE10sDisabledInSafeMode = 3, was removed in bug 1172491.
   kE10sDisabledForAccessibility = 4,
   // kE10sDisabledForMacGfx = 5, was removed in bug 1068674.
   kE10sDisabledForBidi = 6,
   kE10sDisabledForAddons = 7,
   kE10sForceDisabled = 8,
 };
 
-#ifdef XP_WIN
+#if defined(XP_WIN) || defined(XP_MACOSX)
 const char* kAccessibilityLastRunDatePref = "accessibility.lastLoadDate";
 const char* kAccessibilityLoadedLastSessionPref = "accessibility.loadedInLastSession";
-#endif // XP_WIN
-const char* kForceEnableE10sPref = "browser.tabs.remote.force-enable";
-const char* kForceDisableE10sPref = "browser.tabs.remote.force-disable";
-
-#ifdef XP_WIN
+
 static inline uint32_t
 PRTimeToSeconds(PRTime t_usec)
 {
   PRTime usec_per_sec = PR_USEC_PER_SEC;
   return uint32_t(t_usec /= usec_per_sec);
 }
-#endif // XP_WIN
+#endif // XP_WIN || XP_MACOSX
+
+const char* kForceEnableE10sPref = "browser.tabs.remote.force-enable";
+const char* kForceDisableE10sPref = "browser.tabs.remote.force-disable";
+
 
 uint32_t
 MultiprocessBlockPolicy() {
   if (gMultiprocessBlockPolicyInitialized) {
     return gMultiprocessBlockPolicy;
   }
   gMultiprocessBlockPolicyInitialized = true;
 
@@ -4699,17 +4699,17 @@ MultiprocessBlockPolicy() {
 #endif
 
   if (addonsCanDisable && disabledByAddons) {
     gMultiprocessBlockPolicy = kE10sDisabledForAddons;
     return gMultiprocessBlockPolicy;
   }
 
   bool disabledForA11y = false;
-#ifdef XP_WIN
+#if defined(XP_WIN) || defined(XP_MACOSX)
   /**
    * Avoids enabling e10s if accessibility has recently loaded. Performs the
    * following checks:
    * 1) Checks a pref indicating if a11y loaded in the last session. This pref
    * is set in nsBrowserGlue.js. If a11y was loaded in the last session we
    * do not enable e10s in this session.
    * 2) Accessibility stores a last run date (PR_IntervalNow) when it is
    * initialized (see nsBaseWidget.cpp). We check if this pref exists and
@@ -4726,17 +4726,17 @@ MultiprocessBlockPolicy() {
     uint32_t now = PRTimeToSeconds(PR_Now());
     uint32_t difference = now - a11yRunDate;
     if (difference > ONE_WEEK_IN_SECONDS || !a11yRunDate) {
       Preferences::ClearUser(kAccessibilityLastRunDatePref);
     } else {
       disabledForA11y = true;
     }
   }
-#endif // XP_WIN
+#endif // XP_WIN || XP_MACOSX
 
   if (disabledForA11y) {
     gMultiprocessBlockPolicy = kE10sDisabledForAccessibility;
     return gMultiprocessBlockPolicy;
   }
 
   /**
    * Avoids enabling e10s for certain locales that require bidi selection,

--- a/widget/nsBaseWidget.cpp
+++ b/widget/nsBaseWidget.cpp
@@ -164,17 +164,17 @@ nsBaseWidget::nsBaseWidget()
 , mOriginalBounds(nullptr)
 , mClipRectCount(0)
 , mSizeMode(nsSizeMode_Normal)
 , mPopupLevel(ePopupLevelTop)
 , mPopupType(ePopupTypeAny)
 , mUpdateCursor(true)
 , mUseAttachedEvents(false)
 , mIMEHasFocus(false)
-#ifdef XP_WIN
+#if defined(XP_WIN) || defined(XP_MACOSX)
 , mAccessibilityInUseFlag(false)
 #endif
 {
 #ifdef NOISY_WIDGET_LEAKS
   gNumWidgets++;
   printf("WIDGETS+ = %d\n", gNumWidgets);
 #endif
 
@@ -232,17 +232,17 @@ WidgetShutdownObserver::Unregister()
 {
   if (mRegistered) {
     mWidget = nullptr;
     nsContentUtils::UnregisterShutdownObserver(this);
     mRegistered = false;
   }
 }
 
-#ifdef XP_WIN
+#if defined(XP_WIN) || defined(XP_MACOSX)
 // defined in nsAppRunner.cpp
 extern const char* kAccessibilityLastRunDatePref;
 
 static inline uint32_t
 PRTimeToSeconds(PRTime t_usec)
 {
   PRTime usec_per_sec = PR_USEC_PER_SEC;
   return uint32_t(t_usec /= usec_per_sec);
@@ -254,22 +254,16 @@ nsBaseWidget::Shutdown()
 {
   DestroyCompositor();
   FreeShutdownObserver();
 #if defined(XP_WIN) || defined(MOZ_WIDGET_GTK)
   if (sPluginWidgetList) {
     delete sPluginWidgetList;
     sPluginWidgetList = nullptr;
   }
-#if defined(XP_WIN)
-  if (mAccessibilityInUseFlag) {
-    uint32_t now = PRTimeToSeconds(PR_Now());
-    Preferences::SetInt(kAccessibilityLastRunDatePref, now);
-  }
-#endif
 #endif
 }
 
 void nsBaseWidget::DestroyCompositor()
 {
   if (mCompositorBridgeChild) {
     // XXX CompositorBridgeChild and CompositorBridgeParent might be re-created in
     // ClientLayerManager destructor. See bug 1133426.
@@ -1870,18 +1864,22 @@ nsBaseWidget::GetRootAccessible()
   nsPresContext* presContext = presShell->GetPresContext();
   NS_ENSURE_TRUE(presContext->GetContainerWeak(), nullptr);
 
   // Accessible creation might be not safe so use IsSafeToRunScript to
   // make sure it's not created at unsafe times.
   nsCOMPtr<nsIAccessibilityService> accService =
     services::GetAccessibilityService();
   if (accService) {
-#ifdef XP_WIN
-    mAccessibilityInUseFlag = true;
+#if defined(XP_WIN) || defined(XP_MACOSX)
+    if (!mAccessibilityInUseFlag) {
+      mAccessibilityInUseFlag = true;
+      uint32_t now = PRTimeToSeconds(PR_Now());
+      Preferences::SetInt(kAccessibilityLastRunDatePref, now);
+    }
 #endif
     return accService->GetRootDocumentAccessible(presShell, nsContentUtils::IsSafeToRunScript());
   }
 
   return nullptr;
 }
 
 #endif // ACCESSIBILITY

--- a/widget/nsBaseWidget.h
+++ b/widget/nsBaseWidget.h
@@ -543,17 +543,17 @@ protected:
   nsSizeMode        mSizeMode;
   nsPopupLevel      mPopupLevel;
   nsPopupType       mPopupType;
   SizeConstraints   mSizeConstraints;
 
   bool              mUpdateCursor;
   bool              mUseAttachedEvents;
   bool              mIMEHasFocus;
-#ifdef XP_WIN
+#if defined(XP_WIN) || defined(XP_MACOSX)
   bool              mAccessibilityInUseFlag;
 #endif
   static nsIRollupListener* gRollupListener;
 
   // the last rolled up popup. Only set this when an nsAutoRollup is in scope,
   // so it can be cleared automatically.
   static nsIContent* mLastRollup;