2 files changed, 27 insertions, 2 deletions
diff --git a/core/java/android/view/View.java b/core/java/android/view/View.java
index 5a8b265..bac087e 100644
--- a/core/java/android/view/View.java
+++ b/core/java/android/view/View.java
@@ -12872,7 +12872,7 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
                         Interpolator.Result.FREEZE_END) {
                     cache.state = ScrollabilityCache.OFF;
                 } else {
-                    cache.scrollBar.setAlpha(Math.round(values[0]));
+                    cache.scrollBar.mutate().setAlpha(Math.round(values[0]));
                 }
 
                 // This will make the scroll bars inval themselves after
@@ -12882,7 +12882,7 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
             } else {
                 // We're just on -- but we may have been fading before so
                 // reset alpha
-                cache.scrollBar.setAlpha(255);
+                cache.scrollBar.mutate().setAlpha(255);
             }
 
 
diff --git a/core/java/android/widget/ScrollBarDrawable.java b/core/java/android/widget/ScrollBarDrawable.java
index b12c581..6fd90c3 100644
--- a/core/java/android/widget/ScrollBarDrawable.java
+++ b/core/java/android/widget/ScrollBarDrawable.java
@@ -44,6 +44,7 @@ public class ScrollBarDrawable extends Drawable implements Drawable.Callback {
     private boolean mRangeChanged;
     private boolean mAlwaysDrawHorizontalTrack;
     private boolean mAlwaysDrawVerticalTrack;
+    private boolean mMutated;
 
     private int mAlpha = 255;
     private boolean mHasSetAlpha;
@@ -266,6 +267,10 @@ public class ScrollBarDrawable extends Drawable implements Drawable.Callback {
 
     private void propagateCurrentState(Drawable d) {
         if (d != null) {
+            if (mMutated) {
+                d.mutate();
+            }
+
             d.setState(getState());
             d.setCallback(this);
 
@@ -290,6 +295,26 @@ public class ScrollBarDrawable extends Drawable implements Drawable.Callback {
     }
 
     @Override
+    public ScrollBarDrawable mutate() {
+        if (!mMutated && super.mutate() == this) {
+            if (mVerticalTrack != null) {
+                mVerticalTrack.mutate();
+            }
+            if (mVerticalThumb != null) {
+                mVerticalThumb.mutate();
+            }
+            if (mHorizontalTrack != null) {
+                mHorizontalTrack.mutate();
+            }
+            if (mHorizontalThumb != null) {
+                mHorizontalThumb.mutate();
+            }
+            mMutated = true;
+        }
+        return this;
+    }
+
+    @Override
     public void setAlpha(int alpha) {
         mAlpha = alpha;
         mHasSetAlpha = true;