[fenix] Fixes https://github.com/mozilla-mobile/fenix/issues/1186: Make quick actions invisible to screen reader when collapsed.

The buttons in the quick actions sheet are not visible or interactive
when the sheet is collapsed. They should not be visible to AT users
either.

app/src/main/java/org/mozilla/fenix/quickactionsheet/QuickActionSheet.kt

@@ -48,6 +48,17 @@ class QuickActionSheet @JvmOverloads constructor(
 
         handle.setAccessibilityDelegate(HandleAccessibilityDelegate(quickActionSheetBehavior))
 
+        quickActionSheetBehavior.setBottomSheetCallback(object : BottomSheetBehavior.BottomSheetCallback() {
+            override fun onStateChanged(v: View, state: Int) {
+                updateImportantForAccessibility(state)
+            }
+
+            override fun onSlide(p0: View, p1: Float) {
+            }
+        })
+
+        updateImportantForAccessibility(quickActionSheetBehavior.state)
+
         val settings = Settings.getInstance(context)
         if (settings.shouldAutoBounceQuickActionSheet) {
             settings.incrementAutomaticBounceQuickActionSheetCount()
@@ -55,6 +66,14 @@ class QuickActionSheet @JvmOverloads constructor(
         }
     }
 
+    private fun updateImportantForAccessibility(state: Int) {
+        findViewById<LinearLayout>(R.id.quick_action_sheet_buttonbar).importantForAccessibility =
+            if (state == BottomSheetBehavior.STATE_COLLAPSED || state == BottomSheetBehavior.STATE_HIDDEN)
+                View.IMPORTANT_FOR_ACCESSIBILITY_NO_HIDE_DESCENDANTS
+            else
+                View.IMPORTANT_FOR_ACCESSIBILITY_AUTO
+    }
+
     private fun bounceSheet(
         quickActionSheetBehavior: QuickActionSheetBehavior,
         duration: Long = bounceAnimationLength

app/src/main/res/layout/layout_quick_action_sheet.xml

@@ -21,6 +21,7 @@
         android:src="@drawable/ic_drawer_pull_tab"/>
 
     <LinearLayout
+        android:id="@+id/quick_action_sheet_buttonbar"
         android:orientation="horizontal"
         android:layout_gravity="bottom"
         android:layout_width="match_parent"