Use SCREEN Xfermode for keyguard badges; update SeekBar

Plumb through the necessary API features through Drawables and
ImageView but leave it hidden for now pending future API review and
plumbing through the rest of the framework Drawable implementations.

Update SeekBar assets used for keyguard transport control.

Set selected status directly instead of finding views by id.

Bug 10531608
Bug 10784913

Change-Id: Ia38bd04ad1bc26e9e6da1dda8a374c9ba3ceccb3

graphics/java/android/graphics/drawable/BitmapDrawable.java

@@ -28,6 +28,7 @@ import android.graphics.Paint;
 import android.graphics.PixelFormat;
 import android.graphics.Rect;
 import android.graphics.Shader;
+import android.graphics.Xfermode;
 import android.util.AttributeSet;
 import android.util.DisplayMetrics;
 import android.util.LayoutDirection;
@@ -530,6 +531,14 @@ public class BitmapDrawable extends Drawable {
         invalidateSelf();
     }
 
+    /**
+     * @hide Candidate for future API inclusion
+     */
+    public void setXfermode(Xfermode xfermode) {
+        mBitmapState.mPaint.setXfermode(xfermode);
+        invalidateSelf();
+    }
+
     /**
      * A mutable BitmapDrawable still shares its Bitmap with any other Drawable
      * that comes from the same resource.