Fix TaskbarBackgroundRenderer not being applied correctly in 2 cases

- Rename isInAppAndNotStashed to areTaskbarIconsVisibleAndNotStashing,
  and check taskbarViewController.areIconsVisible() accordingly. This
  effectively handles the same as before, but also handles Overview,
  which is not inApp but does have areIconsVisible()
  - This fixes bubble scrim over overview taskbar, as well as showing
    taskbar background behind assistant in 3 button mode.
- Also fix nav bar button dark density changing when applying the
  separate background for assistant

Test: Open bubble and invoke assistant in overview, over IME, inside
an app, over home
Fixes: 266715337

Change-Id: Ie655de7abd1634e2165543d57664d7c7e054a986

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

@@ -60,6 +60,7 @@ public class TaskbarDragLayerController implements TaskbarControllers.LoggableTa
     private AnimatedFloat mNavButtonDarkIntensityMultiplier;
 
     private float mLastSetBackgroundAlpha;
+    private boolean mIsBackgroundDrawnElsewhere;
 
     public TaskbarDragLayerController(TaskbarActivityContext activity,
             TaskbarDragLayer taskbarDragLayer) {
@@ -168,9 +169,23 @@ public class TaskbarDragLayerController implements TaskbarControllers.LoggableTa
         mTaskbarDragLayer.setCornerRoundness(cornerRoundness);
     }
 
+    /**
+     * Set if another controller is temporarily handling background drawing. In this case we:
+     * - Override our background alpha to be 0.
+     * - Keep the nav bar dark intensity assuming taskbar background is at full alpha.
+     */
+    public void setIsBackgroundDrawnElsewhere(boolean isBackgroundDrawnElsewhere) {
+        mIsBackgroundDrawnElsewhere = isBackgroundDrawnElsewhere;
+        mBgOverride.updateValue(mIsBackgroundDrawnElsewhere ? 0 : 1);
+        updateNavBarDarkIntensityMultiplier();
+    }
+
     private void updateNavBarDarkIntensityMultiplier() {
         // Zero out the app-requested dark intensity when we're drawing our own background.
         float effectiveBgAlpha = mLastSetBackgroundAlpha * (1 - mBgOffset.value);
+        if (mIsBackgroundDrawnElsewhere) {
+            effectiveBgAlpha = 1;
+        }
         mNavButtonDarkIntensityMultiplier.updateValue(1 - effectiveBgAlpha);
     }