Bug 1316549 Part 1 - Fix LogicalSideForLineRelativeDir() for eLineRelativeDirLeft/Right. r=jfkthame

According to the spec, 6.4. Abstract-to-Physical Mappings,
line-left/line-right are equal to inline-start/inline-end when the direction
is the same. So we should use IsBlockLTR() instead of IsLineInverted().

https://drafts.csswg.org/css-writing-modes-3/#logical-to-physical

MozReview-Commit-ID: 7onE0SuHtdj

--HG--
extra : rebase_source : df0083ed7e28469a2343a8607840585e93502b80

layout/generic/WritingModes.h

@@ -463,7 +463,7 @@ public:
   {
     auto side = static_cast<LogicalSide>(aDir);
     if (IsInline(side)) {
-      return !IsInlineReversed() ? side : GetOppositeSide(side);
+      return IsBidiLTR() ? side : GetOppositeSide(side);
     }
     return !IsLineInverted() ? side : GetOppositeSide(side);
   }