Improve the rendering speed of the lock screen by reporting the appropriate opacity for the background wallpaper.

policy/com/android/internal/policy/impl/LockPatternKeyguardView.java

@@ -590,9 +590,11 @@ public class LockPatternKeyguardView extends KeyguardViewBase {
      */
     static private class FastBitmapDrawable extends Drawable {
         private Bitmap mBitmap;
+        private int mOpacity;
 
         private FastBitmapDrawable(Bitmap bitmap) {
             mBitmap = bitmap;
+            mOpacity = mBitmap.hasAlpha() ? PixelFormat.TRANSLUCENT : PixelFormat.OPAQUE;
         }
 
         @Override
@@ -606,7 +608,7 @@ public class LockPatternKeyguardView extends KeyguardViewBase {
 
         @Override
         public int getOpacity() {
-            return PixelFormat.TRANSLUCENT;
+            return mOpacity;
         }
 
         @Override