[LayoutNG] Fix off-by-one hit test failure at vertical-rl line edges

The hit test "point" is not really a point, but a pixel with 1px width
and height. Ignoring this leads to off-by-one errors when converting
a physical point into logical in vertical-rl writing mode.

This patch fixes the issue by using 1px width and height in the
conversion, instead of 0.

Note: This patch contains an all-pass NG baseline because the legacy
baseline contains a failure line.

Bug: 811502
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ie3f01469b4902c3c9647d40be92ccb9c26467f0d
Reviewed-on: https://chromium-review.googlesource.com/1150814
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578178}

third_party/WebKit/LayoutTests/FlagExpectations/enable-blink-features=LayoutNG

@@ -583,7 +583,6 @@ crbug.com/591099 fast/writing-mode/border-image-vertical-lr.html [ Failure ]
 crbug.com/591099 fast/writing-mode/border-radius-clipping-vertical-lr.html [ Failure ]
 crbug.com/714962 fast/writing-mode/border-styles-vertical-lr.html [ Failure ]
 crbug.com/591099 fast/writing-mode/fieldsets.html [ Failure ]
-crbug.com/714962 fast/writing-mode/flipped-blocks-hit-test-line-edges.html [ Failure ]
 crbug.com/591099 fast/writing-mode/percentage-height-orthogonal-writing-modes.html [ Failure ]
 crbug.com/591099 fast/writing-mode/table-percent-width-quirk.html [ Pass ]
 crbug.com/591099 fullscreen/full-screen-with-flex-item.html [ Failure ]

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/fast/writing-mode/flipped-blocks-hit-test-line-edges-expected.txt

+Lorem ipsum dolor sit amet
+PASS: offset at (100,105) was 4.
+PASS: offset at (160,105) was 5.
+PASS: offset at (100,104) was 10.
+PASS: offset at (160,104) was 11.
+PASS: offset at (60,26) was 24.
+PASS: offset at (160,26) was 26.
+PASS: offset at (60,25) was 24.
+PASS: offset at (160,25) was 26.
+PASS: offset at (60,24) was 24.
+PASS: offset at (160,24) was 26.
+

third_party/blink/renderer/core/paint/ng/ng_paint_fragment.cc

@@ -478,7 +478,9 @@ PositionWithAffinity NGPaintFragment::PositionForPointInInlineLevelBox(
   DCHECK(!PhysicalFragment().IsBlockFlow());
 
   const NGLogicalOffset logical_point = point.ConvertToLogical(
-      Style().GetWritingMode(), Style().Direction(), Size(), NGPhysicalSize());
+      Style().GetWritingMode(), Style().Direction(), Size(),
+      // |point| is actually a pixel with size 1x1.
+      NGPhysicalSize(LayoutUnit(1), LayoutUnit(1)));
   const LayoutUnit inline_point = logical_point.inline_offset;
 
   // Stores the closest child before |point| in the inline direction. Used if we
@@ -541,7 +543,9 @@ PositionWithAffinity NGPaintFragment::PositionForPointInInlineFormattingContext(
   DCHECK(ToNGPhysicalBoxFragment(PhysicalFragment()).ChildrenInline());
 
   const NGLogicalOffset logical_point = point.ConvertToLogical(
-      Style().GetWritingMode(), Style().Direction(), Size(), NGPhysicalSize());
+      Style().GetWritingMode(), Style().Direction(), Size(),
+      // |point| is actually a pixel with size 1x1.
+      NGPhysicalSize(LayoutUnit(1), LayoutUnit(1)));
   const LayoutUnit block_point = logical_point.block_offset;
 
   // Stores the closest line box child above |point| in the block direction.