Fix scrollbar-gutter when LayoutNG is disabled

Update LayoutBlockFlow::DetermineLogicalLeftPositionForChild to
correctly take into account all the cases where the width of the
logical left scrollbar may be different from 0.

This fixes a problem where the "both" value of scrollbar-gutter
was producing the wrong layout when LayoutNG was disabled.

Bug: 710214
Change-Id: If3481ff2486fc3a7a447b892edc8ef98fa658f1c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2459793Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Felipe Erias Morandeira <felipeerias@gmail.com>
Cr-Commit-Position: refs/heads/master@{#815060}

third_party/blink/renderer/core/layout/layout_block_flow.cc

@@ -690,10 +690,16 @@ void LayoutBlockFlow::DetermineLogicalLeftPositionForChild(LayoutBox& child) {
   NOT_DESTROYED();
   LayoutUnit start_position = BorderStart() + PaddingStart();
   LayoutUnit initial_start_position = start_position;
-  start_position -= LogicalLeftScrollbarWidth();
   LayoutUnit total_available_logical_width =
       BorderAndPaddingLogicalWidth() + AvailableLogicalWidth();
 
+  if (StyleRef().IsHorizontalWritingMode() &&
+      !StyleRef().IsLeftToRightDirection()) {
+    start_position -= LogicalLeftScrollbarWidth();
+  } else {
+    start_position += LogicalLeftScrollbarWidth();
+  }
+
   LayoutUnit child_margin_start = MarginStartForChild(child);
   LayoutUnit new_position = start_position + child_margin_start;
 

third_party/blink/web_tests/FlagExpectations/disable-layout-ng

@@ -434,12 +434,6 @@ crbug.com/591099 external/wpt/css/css-overflow/webkit-line-clamp-013.html [ Fail
 crbug.com/591099 external/wpt/css/css-overflow/webkit-line-clamp-014.html [ Failure ]
 crbug.com/591099 external/wpt/css/css-overflow/webkit-line-clamp-027.html [ Failure ]
 
-# More than one scrollbar gutter (i.e. the "both" value of scrollbar-gutter)
-crbug.com/710214 wpt_internal/css/css-overflow/scrollbar-gutter-004.html [ Failure ]
-crbug.com/710214 wpt_internal/css/css-overflow/scrollbar-gutter-005.html [ Failure ]
-crbug.com/710214 wpt_internal/css/css-overflow/scrollbar-gutter-009.html [ Failure ]
-crbug.com/710214 wpt_internal/css/css-overflow/scrollbar-gutter-010.html [ Failure ]
-
 # White space, absolute position and paint timing failures from June 5, 2020
 crbug.com/591099 external/wpt/paint-timing/fcp-only/fcp-pseudo-element-visibility.html [ Failure ]
 crbug.com/591099 external/wpt/css/css-position/position-absolute-center-001.tentative.html [ Failure ]