Revert "Revert "Updating the scroll calculation from recyclerView to avoid view inflation""

Test: ABTD
https://android-build.googleplex.com/builds/abtd/run/L52600000956969786

This reverts commit cee6ddf3deaed339e6d6df7f1682c725a00197b9.

Reason for revert: Fixed in ag/20239136

Change-Id: I0e8446e66d9a86a94b40fcbd6de14da07abe8e5c
diff --git a/src/com/android/launcher3/FastScrollRecyclerView.java b/src/com/android/launcher3/FastScrollRecyclerView.java
index 747b755..2f927d3 100644
--- a/src/com/android/launcher3/FastScrollRecyclerView.java
+++ b/src/com/android/launcher3/FastScrollRecyclerView.java
@@ -24,7 +24,6 @@
 import android.view.accessibility.AccessibilityNodeInfo;
 
 import androidx.annotation.Nullable;
-import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
 
 import com.android.launcher3.compat.AccessibilityManagerCompat;
@@ -92,8 +91,7 @@
     protected int getAvailableScrollHeight() {
         // AvailableScrollHeight = Total height of the all items - first page height
         int firstPageHeight = getMeasuredHeight() - getPaddingTop() - getPaddingBottom();
-        int totalHeightOfAllItems = getItemsHeight(/* untilIndex= */ getAdapter().getItemCount());
-        int availableScrollHeight = totalHeightOfAllItems - firstPageHeight;
+        int availableScrollHeight = computeVerticalScrollRange() - firstPageHeight;
         return Math.max(0, availableScrollHeight);
     }
 
@@ -146,10 +144,7 @@
 
         // IF scroller is at the very top OR there is no scroll bar because there is probably not
         // enough items to scroll, THEN it's okay for the container to be pulled down.
-        if (getCurrentScrollY() == 0) {
-            return true;
-        }
-        return getAdapter() == null || getAdapter().getItemCount() == 0;
+        return computeVerticalScrollOffset() == 0;
     }
 
     /**
@@ -160,53 +155,6 @@
     }
 
     /**
-     * @return the scroll top of this recycler view.
-     */
-    public int getCurrentScrollY() {
-        Adapter adapter = getAdapter();
-        if (adapter == null) {
-            return -1;
-        }
-        if (adapter.getItemCount() == 0 || getChildCount() == 0) {
-            return -1;
-        }
-
-        int itemPosition = NO_POSITION;
-        View child = null;
-
-        LayoutManager layoutManager = getLayoutManager();
-        if (layoutManager instanceof LinearLayoutManager) {
-            // Use the LayoutManager as the source of truth for visible positions. During
-            // animations, the view group child may not correspond to the visible views that appear
-            // at the top.
-            itemPosition = ((LinearLayoutManager) layoutManager).findFirstVisibleItemPosition();
-            child = layoutManager.findViewByPosition(itemPosition);
-        }
-
-        if (child == null) {
-            // If the layout manager returns null for any reason, which can happen before layout
-            // has occurred for the position, then look at the child of this view as a ViewGroup.
-            child = getChildAt(0);
-            itemPosition = getChildAdapterPosition(child);
-        }
-        if (itemPosition == NO_POSITION) {
-            return -1;
-        }
-        return getPaddingTop() + getItemsHeight(itemPosition)
-                - layoutManager.getDecoratedTop(child);
-    }
-
-    /**
-     * Returns the sum of the height, in pixels, of this list adapter's items from index
-     * 0 (inclusive) until {@code untilIndex} (exclusive). If untilIndex is same as the itemCount,
-     * it returns the full height of all the items.
-     *
-     * <p>If the untilIndex is larger than the total number of items in this adapter, returns the
-     * sum of all items' height.
-     */
-    protected abstract int getItemsHeight(int untilIndex);
-
-    /**
      * Maps the touch (from 0..1) to the adapter position that should be visible.
      * <p>Override in each subclass of this base class.
      */