For mozilla-mobile#9932 - Introduce an offset in ExpandableLayout

If the menu starts as collapsed and it has a sticky footer set the bottom item
until which the menu should be collapsed must be shown on top of the sticky
item's view. For this the entire menu has to have as offset the height of the
sticky item's view.

components/browser/menu/src/main/java/mozilla/components/browser/menu/BrowserMenu.kt

@@ -128,11 +128,15 @@ open class BrowserMenu internal constructor(
             menuPositioningData.inferredMenuPlacement is BrowserMenuPlacement.AnchoredToBottom.ManualAnchoring) {
 
             val collapsingMenuIndexLimit = adapter.visibleItems.indexOfFirst { it.isCollapsingMenuLimit }
+            val stickyItemHeight = menuList?.layoutManager
+                ?.getChildAt(adapter.visibleItems.indexOfLast { it.isSticky })
+                ?.height ?: 0
 
             if (collapsingMenuIndexLimit > 0) {
                 return ExpandableLayout.wrapContentInExpandableView(
                     view,
-                    collapsingMenuIndexLimit
+                    collapsingMenuIndexLimit,
+                    offset = stickyItemHeight
                 ) { dismiss() }
             }
         } else {

components/browser/menu/src/main/java/mozilla/components/browser/menu/view/ExpandableLayout.kt

@@ -35,6 +35,9 @@ internal class ExpandableLayout private constructor(context: Context) : FrameLay
     @VisibleForTesting
     internal lateinit var wrappedView: ViewGroup
 
+    @VisibleForTesting
+    internal var heightOffset: Int = 0
+
     /**
      * Listener of touches in the empty space left by the collapsed view.
      */
@@ -312,6 +315,7 @@ internal class ExpandableLayout private constructor(context: Context) : FrameLay
         }
 
         var result = 0
+        result += heightOffset
         result += wrappedView.marginTop
         result += wrappedView.marginBottom
         result += wrappedView.paddingTop
@@ -362,6 +366,7 @@ internal class ExpandableLayout private constructor(context: Context) : FrameLay
         internal fun wrapContentInExpandableView(
             contentView: ViewGroup,
             lastVisibleItemIndexWhenCollapsed: Int = Int.MAX_VALUE,
+            offset: Int = 0,
             blankTouchListener: (() -> Unit)? = null
         ): ExpandableLayout {
 
@@ -376,6 +381,7 @@ internal class ExpandableLayout private constructor(context: Context) : FrameLay
             expandableView.addView(contentView, params)
 
             expandableView.wrappedView = contentView
+            expandableView.heightOffset = offset
             expandableView.blankTouchListener = blankTouchListener
             expandableView.lastVisibleItemIndexWhenCollapsed = lastVisibleItemIndexWhenCollapsed