Add local wallpaper color extraction to folder backgrounds.

- Starts listening to local wallpaper colors as soon as folder
  is positioned.
- The folder open animation already has a background color
  animator.
- For simplicity, folder open animation always starts
  first, and then we cancel its background color animator,
  and start a new animator to the extracted color.
- setAutoCancel would be handy here, but it does not work, will
  track in a separate bug.
- Since folders are reused, we clear our the color extractor on
  folder close.

Bug: 175329686
Test: multiple folders on rainbow background
      open each folder, ensure bg animates to proper color
Change-Id: Ie0f2c0632fa2361f7710ba247d74f882620dec16

src/com/android/launcher3/AbstractFloatingView.java

@@ -39,6 +39,7 @@ import com.android.launcher3.anim.PendingAnimation;
 import com.android.launcher3.util.TouchController;
 import com.android.launcher3.views.ActivityContext;
 import com.android.launcher3.views.BaseDragLayer;
+import com.android.launcher3.widget.LocalColorExtractor;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -108,12 +109,21 @@ public abstract class AbstractFloatingView extends LinearLayout implements Touch
 
     protected boolean mIsOpen;
 
+    // Index used to get background color when using local wallpaper color extraction.
+    protected int mColorExtractionIndex;
+
     public AbstractFloatingView(Context context, AttributeSet attrs) {
         super(context, attrs);
+        init(context);
     }
 
     public AbstractFloatingView(Context context, AttributeSet attrs, int defStyleAttr) {
         super(context, attrs, defStyleAttr);
+        init(context);
+    }
+
+    private void init(Context context) {
+        mColorExtractionIndex = LocalColorExtractor.getColorIndex(context);
     }
 
     /**