Predictive back: widget to all apps

This CL adds a layer of OnBackPressedHanlderRouter to Launcher:
1. 4 OnBackPressedHandler(s) are added in such order: auto cancel action mode handler, drag handler, view handler and state handler
2. first handler who can handle back will handle the entire back gesture
3. Let WidgetsFullSheet to handle widget to all apps transition

Bug: b/260956481
Test: manual
Change-Id: Idbce3dcec746226dd68aaabaddc8fe01334e9673

src/com/android/launcher3/AbstractFloatingView.java

@@ -46,7 +46,8 @@ import java.lang.annotation.RetentionPolicy;
 /**
  * Base class for a View which shows a floating UI on top of the launcher UI.
  */
-public abstract class AbstractFloatingView extends LinearLayout implements TouchController {
+public abstract class AbstractFloatingView extends LinearLayout implements TouchController,
+        OnBackPressedHandler {
 
     @IntDef(flag = true, value = {
             TYPE_FOLDER,
@@ -165,12 +166,16 @@ public abstract class AbstractFloatingView extends LinearLayout implements Touch
 
     protected abstract boolean isOfType(@FloatingViewType int type);
 
-    /** @return Whether the back is consumed. If false, Launcher will handle the back as well. */
-    public boolean onBackPressed() {
-        close(true);
+    /** Return true if this view can consume back press. */
+    public boolean canHandleBack() {
         return true;
     }
 
+    @Override
+    public void onBackInvoked() {
+        close(true);
+    }
+
     @Override
     public boolean onControllerTouchEvent(MotionEvent ev) {
         return false;