Fix texture memory regression system_health.memory_desktop

This reverts the line to before crrev.com/c/1826994
(see crrev.com/c/1826994/3/third_party/blink/renderer/core/paint/paint_layer_scrollable_area.cc#b2680).

Still not sure how the visual rect of composited overlay scrollbar
affects texture memory. The visual rect doesn't affect paint or raster
invalidation.

Bug: 1011996
Change-Id: I20f2c9bddd2e6a0aff254f598ba0f16b3d6d5738
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1847942
Auto-Submit: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705417}

third_party/blink/renderer/core/paint/paint_layer_scrollable_area.cc

@@ -2689,7 +2689,11 @@ static IntRect InvalidatePaintOfScrollbarIfNeeded(
   bool is_overlay = scrollbar && scrollbar->IsOverlayScrollbar();
 
   IntRect new_visual_rect;
-  if (scrollbar)
+  // Calculate visual rect of the scrollbar, except overlay composited
+  // scrollbars because we invalidate the graphics layer only.
+  // TODO(wangxianzhu): Investigate how non-empty visual rect of composited
+  // scrollbar affects GPU texture memory (http://crbug.com/1011996).
+  if (scrollbar && !(graphics_layer && is_overlay))
     new_visual_rect = scrollbar->FrameRect();
 
   if (needs_paint_invalidation && graphics_layer) {