diff --git a/include/private/SkIDChangeListener.h b/include/private/SkIDChangeListener.h
index 7cf0412..f7a5900 100644
--- a/include/private/SkIDChangeListener.h
+++ b/include/private/SkIDChangeListener.h
@@ -49,23 +49,23 @@
          * Add a new listener to the list. It must not already be deregistered. Also clears out
          * previously deregistered listeners.
          */
-        void add(sk_sp<SkIDChangeListener> listener, bool singleThreaded = false);
+        void add(sk_sp<SkIDChangeListener> listener) SK_EXCLUDES(fMutex);
 
         /**
          * The number of registered listeners (including deregisterd listeners that are yet-to-be
          * removed.
          */
-        int count();
+        int count() const SK_EXCLUDES(fMutex);
 
         /** Calls changed() on all listeners that haven't been deregistered and resets the list. */
-        void changed(bool singleThreaded = false);
+        void changed() SK_EXCLUDES(fMutex);
 
         /** Resets without calling changed() on the listeners. */
-        void reset(bool singleThreaded = false);
+        void reset() SK_EXCLUDES(fMutex);
 
     private:
-        SkMutex fMutex;
-        SkTDArray<SkIDChangeListener*> fListeners;  // pointers are reffed
+        mutable SkMutex fMutex;
+        SkTDArray<SkIDChangeListener*> fListeners SK_GUARDED_BY(fMutex);  // pointers are reffed
     };
 
 private:
diff --git a/src/core/SkIDChangeListener.cpp b/src/core/SkIDChangeListener.cpp
index 954b468..6310cd9 100644
--- a/src/core/SkIDChangeListener.cpp
+++ b/src/core/SkIDChangeListener.cpp
@@ -34,61 +34,41 @@
     }
 }
 
-void List::add(sk_sp<SkIDChangeListener> listener, bool singleThreaded) {
+void List::add(sk_sp<SkIDChangeListener> listener) {
     if (!listener) {
         return;
     }
     SkASSERT(!listener->shouldDeregister());
 
-    auto add = [&] {
-        // Clean out any stale listeners before we append the new one.
-        for (int i = 0; i < fListeners.count(); ++i) {
-            if (fListeners[i]->shouldDeregister()) {
-                fListeners[i]->unref();
-                fListeners.removeShuffle(i--);  // No need to preserve the order after i.
-            }
+    SkAutoMutexExclusive lock(fMutex);
+    // Clean out any stale listeners before we append the new one.
+    for (int i = 0; i < fListeners.count(); ++i) {
+        if (fListeners[i]->shouldDeregister()) {
+            fListeners[i]->unref();
+            fListeners.removeShuffle(i--);  // No need to preserve the order after i.
         }
-        *fListeners.append() = listener.release();
-    };
-
-    if (singleThreaded) {
-        add();
-    } else {
-        SkAutoMutexExclusive lock(fMutex);
-        add();
     }
+    *fListeners.append() = listener.release();
 }
 
-int List::count() {
+int List::count() const {
     SkAutoMutexExclusive lock(fMutex);
     return fListeners.count();
 }
 
-void List::changed(bool singleThreaded) {
-    auto visit = [this]() {
-        for (SkIDChangeListener* listener : fListeners) {
-            if (!listener->shouldDeregister()) {
-                listener->changed();
-            }
-            // Listeners get at most one shot, so whether these triggered or not, blow them away.
-            listener->unref();
+void List::changed() {
+    SkAutoMutexExclusive lock(fMutex);
+    for (SkIDChangeListener* listener : fListeners) {
+        if (!listener->shouldDeregister()) {
+            listener->changed();
         }
-        fListeners.reset();
-    };
-
-    if (singleThreaded) {
-        visit();
-    } else {
-        SkAutoMutexExclusive lock(fMutex);
-        visit();
+        // Listeners get at most one shot, so whether these triggered or not, blow them away.
+        listener->unref();
     }
+    fListeners.reset();
 }
 
-void List::reset(bool singleThreaded) {
-    if (singleThreaded) {
-        fListeners.unrefAll();
-    } else {
-        SkAutoMutexExclusive lock(fMutex);
-        fListeners.unrefAll();
-    }
+void List::reset() {
+    SkAutoMutexExclusive lock(fMutex);
+    fListeners.unrefAll();
 }
diff --git a/src/core/SkPathRef.cpp b/src/core/SkPathRef.cpp
index 2ece69a..1244801 100644
--- a/src/core/SkPathRef.cpp
+++ b/src/core/SkPathRef.cpp
@@ -490,16 +490,14 @@
     if (this == gEmpty) {
         return;
     }
-    bool singleThreaded = this->unique();
-    fGenIDChangeListeners.add(std::move(listener), singleThreaded);
+    fGenIDChangeListeners.add(std::move(listener));
 }
 
 int SkPathRef::genIDChangeListenerCount() { return fGenIDChangeListeners.count(); }
 
 // we need to be called *before* the genID gets changed or zerod
 void SkPathRef::callGenIDChangeListeners() {
-    bool singleThreaded = this->unique();
-    fGenIDChangeListeners.changed(singleThreaded);
+    fGenIDChangeListeners.changed();
 }
 
 SkRRect SkPathRef::getRRect() const {
diff --git a/src/core/SkPixelRef.cpp b/src/core/SkPixelRef.cpp
index 71237e6..04a6699 100644
--- a/src/core/SkPixelRef.cpp
+++ b/src/core/SkPixelRef.cpp
@@ -79,23 +79,21 @@
         return;
     }
     SkASSERT(!listener->shouldDeregister());
-    bool singleThreaded = this->unique();
-    fGenIDChangeListeners.add(std::move(listener), singleThreaded);
+    fGenIDChangeListeners.add(std::move(listener));
 }
 
 // we need to be called *before* the genID gets changed or zerod
 void SkPixelRef::callGenIDChangeListeners() {
-    bool singleThreaded = this->unique();
     // We don't invalidate ourselves if we think another SkPixelRef is sharing our genID.
     if (this->genIDIsUnique()) {
-        fGenIDChangeListeners.changed(singleThreaded);
+        fGenIDChangeListeners.changed();
         if (fAddedToCache.exchange(false)) {
             SkNotifyBitmapGenIDIsStale(this->getGenerationID());
         }
     } else {
         // Listeners get at most one shot, so even though these weren't triggered or not, blow them
         // away.
-        fGenIDChangeListeners.reset(singleThreaded);
+        fGenIDChangeListeners.reset();
     }
 }
 
diff --git a/src/image/SkImage_Lazy.cpp b/src/image/SkImage_Lazy.cpp
index e3c9d14..2278336 100644
--- a/src/image/SkImage_Lazy.cpp
+++ b/src/image/SkImage_Lazy.cpp
@@ -503,7 +503,6 @@
 }
 
 void SkImage_Lazy::addUniqueIDListener(sk_sp<SkIDChangeListener> listener) const {
-    bool singleThreaded = this->unique();
-    fUniqueIDListeners.add(std::move(listener), singleThreaded);
+    fUniqueIDListeners.add(std::move(listener));
 }
 #endif