Consider text alignment and direction when computing the left offset for horizontal writing modes.

Source/core/rendering/RenderBlockLineLayout.cpp

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All right reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 549 matching lines @@
             }
             expansionOpportunityCount -= opportunitiesInRun;
             if (!expansionOpportunityCount)
                 break;
         }
     }
 }
 
 void RenderBlockFlow::updateLogicalWidthForAlignment(const ETextAlign& textAlign, const RootInlineBox* rootInlineBox, BidiRun* trailingSpaceRun, float& logicalLeft, float& totalLogicalWidth, float& availableLogicalWidth, int expansionOpportunityCount)
 {
-    TextDirection direction;
-    if (rootInlineBox && rootInlineBox->renderer()->style()->unicodeBidi() == Plaintext)
-        direction = rootInlineBox->direction();
-    else
-        direction = style()->direction();
-
     // Armed with the total width of the line (without justification),
     // we now examine our text-align property in order to determine where to position the
     // objects horizontally. The total width of the line can be increased if we end up
     // justifying text.
-    switch (textAlign) {
+    switch (simplifiedTextAlign(textAlign, rootInlineBox)) {
     case LEFT:
-    case WEBKIT_LEFT:
         updateLogicalWidthForLeftAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         break;
     case RIGHT:
-    case WEBKIT_RIGHT:
         updateLogicalWidthForRightAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         break;
     case CENTER:
-    case WEBKIT_CENTER:
         updateLogicalWidthForCenterAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         break;
     case JUSTIFY:
         adjustInlineDirectionLineBounds(expansionOpportunityCount, logicalLeft, availableLogicalWidth);
         if (expansionOpportunityCount) {
             if (trailingSpaceRun) {
                 totalLogicalWidth -= trailingSpaceRun->m_box->logicalWidth();
                 trailingSpaceRun->m_box->setLogicalWidth(0);
             }
-            break;
+        } else {
+            ETextAlign adjustedTextAlign = style()->isLeftToRightDirection() ? LEFT : RIGHT;
+            updateLogicalWidthForAlignment(adjustedTextAlign, rootInlineBox, trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth, expansionOpportunityCount);
         }
-        // Fall through
-    case TASTART:
-        if (direction == LTR)
-            updateLogicalWidthForLeftAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
-        else
-            updateLogicalWidthForRightAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
         break;
-    case TAEND:
-        if (direction == LTR)
-            updateLogicalWidthForRightAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
-        else
-            updateLogicalWidthForLeftAlignedBlock(style()->isLeftToRightDirection(), trailingSpaceRun, logicalLeft, totalLogicalWidth, availableLogicalWidth);
+    default:
+        ASSERT_NOT_REACHED();
         break;
     }
 }
 
 static void updateLogicalInlinePositions(RenderBlockFlow* block, float& lineLogicalLeft, float& lineLogicalRight, float& availableLogicalWidth, bool firstLine, IndentTextOrNot shouldIndentText, LayoutUnit boxLogicalHeight)
 {
     LayoutUnit lineLogicalHeight = block->minLineHeightForReplacedRenderer(firstLine, boxLogicalHeight);
     lineLogicalLeft = block->logicalLeftOffsetForLine(block->logicalHeight(), shouldIndentText == IndentText, lineLogicalHeight);
     // FIXME: This shouldn't be pixel snapped once multicolumn layout has been updated to correctly carry over subpixel values.
     // https://bugs.webkit.org/show_bug.cgi?id=105461
@@ skipping 1621 matching lines @@
     lineGridBox->alignBoxesInBlockDirection(logicalHeight(), textBoxDataMap, verticalPositionCache);
 
     setLineGridBox(lineGridBox);
 
     // FIXME: If any of the characteristics of the box change compared to the old one, then we need to do a deep dirtying
     // (similar to what happens when the page height changes). Ideally, though, we only do this if someone is actually snapping
     // to this grid.
 }
 
 }