Move taskbar to be closer to QSB

- Offset taskbar to be halfway between QSB and bottom of the screen.
- Add taskbar translationY state property to animate when going
  between launcher and an app.
- Draw the taskbar background in TaskbarContainerView instead of
  TaskbarView so it stays pinned to the bottom as TaskbarView
  translates up. If we want to have a background behind the
  taskbar on home, this should move back to TaskbarView so that
  the drawing can be shared by mTaskbarViewOnHome.

Test: visually on home screen, translates when entering and
exiting an app

Bug: 182981881
Bug: 171917176
Change-Id: I44f8b2c770074f7f015dcccbc2befd3453811193

quickstep/src/com/android/launcher3/taskbar/TaskbarAnimationController.java

@@ -50,6 +50,10 @@ public class TaskbarAnimationController {
     private final AnimatedFloat mTaskbarScaleForLauncherState = new AnimatedFloat(
             this::updateScale);
 
+    // TranslationY.
+    private final AnimatedFloat mTaskbarTranslationYForLauncherState = new AnimatedFloat(
+            this::updateTranslationY);
+
     public TaskbarAnimationController(BaseQuickstepLauncher launcher,
             TaskbarController.TaskbarAnimationControllerCallbacks taskbarCallbacks) {
         mLauncher = launcher;
@@ -81,6 +85,10 @@ public class TaskbarAnimationController {
         return mTaskbarScaleForLauncherState;
     }
 
+    protected AnimatedFloat getTaskbarTranslationYForLauncherState() {
+        return mTaskbarTranslationYForLauncherState;
+    }
+
     protected Animator createAnimToBackgroundAlpha(float toAlpha, long duration) {
         return mTaskbarBackgroundAlpha.animateToValue(mTaskbarBackgroundAlpha.value, toAlpha)
                 .setDuration(duration);
@@ -95,6 +103,7 @@ public class TaskbarAnimationController {
         mTaskbarCallbacks.updateTaskbarBackgroundAlpha(mTaskbarBackgroundAlpha.value);
         updateVisibilityAlpha();
         updateScale();
+        updateTranslationY();
     }
 
     private void updateVisibilityAlpha() {
@@ -120,6 +129,15 @@ public class TaskbarAnimationController {
         mTaskbarCallbacks.updateTaskbarScale(scale);
     }
 
+    private void updateTranslationY() {
+        // We use mTaskbarBackgroundAlpha as a proxy for whether Launcher is resumed/paused, the
+        // assumption being that Taskbar should always be at translationY 0f regardless of the
+        // current LauncherState if Launcher is paused.
+        float translationY = mTaskbarTranslationYForLauncherState.value;
+        translationY = Utilities.mapRange(mTaskbarBackgroundAlpha.value, translationY, 0f);
+        mTaskbarCallbacks.updateTaskbarTranslationY(translationY);
+    }
+
     private void setNavBarButtonAlpha(float navBarAlpha) {
         SystemUiProxy.INSTANCE.get(mLauncher).setNavBarButtonAlpha(navBarAlpha, false);
     }