[CSS Grid Layout] Fix positioned grid children position and size

Source/core/rendering/RenderBox.cpp

Index: Source/core/rendering/RenderBox.cpp
diff --git a/Source/core/rendering/RenderBox.cpp b/Source/core/rendering/RenderBox.cpp
index 14b62cf4e6fde8e87eab1fe29ee2b785d199c97a..d72a527411d9ae371a875b2e96b82558038d27cc 100644
--- a/Source/core/rendering/RenderBox.cpp
+++ b/Source/core/rendering/RenderBox.cpp
@@ -72,6 +72,8 @@ typedef WTF::HashMap<const RenderBox*, LayoutUnit> OverrideSizeMap;
 // FIXME: Move these into RenderBoxRareData.
 static OverrideSizeMap* gOverrideContainingBlockLogicalHeightMap = 0;
 static OverrideSizeMap* gOverrideContainingBlockLogicalWidthMap = 0;
+static OverrideSizeMap* gExtraInlineOffsetMap = 0;
+static OverrideSizeMap* gExtraBlockOffsetMap = 0;
 
 
 // Size of border belt for autoscroll. When mouse pointer in border belt,
@@ -103,6 +105,7 @@ void RenderBox::willBeDestroyed()
 {
     clearOverrideSize();
     clearContainingBlockOverrideSize();
+    clearExtraInlineAndBlockOffests();
 
     RenderBlock::removePercentHeightDescendantIfNeeded(this);
 
@@ -1019,6 +1022,38 @@ void RenderBox::clearOverrideContainingBlockContentLogicalHeight()
         gOverrideContainingBlockLogicalHeightMap->remove(this);
 }
 
+LayoutUnit RenderBox::extraInlineOffset() const
+{
+    return gExtraInlineOffsetMap ? gExtraInlineOffsetMap->get(this) : LayoutUnit(0);
+}
+
+LayoutUnit RenderBox::extraBlockOffset() const
+{
+    return gExtraBlockOffsetMap ? gExtraBlockOffsetMap->get(this) : LayoutUnit(0);
+}
+
+void RenderBox::setExtraInlineOffset(LayoutUnit inlineOffest)
+{
+    if (!gExtraInlineOffsetMap)
+        gExtraInlineOffsetMap = new OverrideSizeMap;
+    gExtraInlineOffsetMap->set(this, inlineOffest);
+}
+
+void RenderBox::setExtraBlockOffset(LayoutUnit blockOffest)
+{
+    if (!gExtraBlockOffsetMap)
+        gExtraBlockOffsetMap = new OverrideSizeMap;
+    gExtraBlockOffsetMap->set(this, blockOffest);
+}
+
+void RenderBox::clearExtraInlineAndBlockOffests()
+{
+    if (gExtraInlineOffsetMap)
+        gExtraInlineOffsetMap->remove(this);
+    if (gExtraBlockOffsetMap)
+        gExtraBlockOffsetMap->remove(this);
+}
+
 LayoutUnit RenderBox::adjustBorderBoxLogicalWidthForBoxSizing(LayoutUnit width) const
 {
     LayoutUnit bordersPlusPadding = borderAndPaddingLogicalWidth();
@@ -2616,6 +2651,9 @@ LayoutUnit RenderBox::containingBlockLogicalWidthForPositioned(const RenderBoxMo
         }
     }
 
+    if (hasOverrideContainingBlockLogicalWidth())
+        return overrideContainingBlockContentLogicalWidth();
+
     if (containingBlock->isBox())
         return toRenderBox(containingBlock)->clientLogicalWidth();
 
@@ -2656,6 +2694,9 @@ LayoutUnit RenderBox::containingBlockLogicalHeightForPositioned(const RenderBoxM
         }
     }
 
+    if (hasOverrideContainingBlockLogicalHeight())
+        return overrideContainingBlockContentLogicalHeight();
+
     if (containingBlock->isBox()) {
         const RenderBlock* cb = containingBlock->isRenderBlock() ?
             toRenderBlock(containingBlock) : containingBlock->containingBlock();
@@ -2842,6 +2883,9 @@ void RenderBox::computePositionedLogicalWidth(LogicalExtentComputedValues& compu
         }
     }
 
+    if (!style()->hasStaticInlinePosition(isHorizontal))
+        computedValues.m_position += extraInlineOffset();
+
     computedValues.m_extent += bordersPlusPadding;
 }
 
@@ -3141,6 +3185,9 @@ void RenderBox::computePositionedLogicalHeight(LogicalExtentComputedValues& comp
         }
     }
 
+    if (!style()->hasStaticBlockPosition(isHorizontalWritingMode()))
+        computedValues.m_position += extraBlockOffset();
+
     // Set final height value.
     computedValues.m_extent += bordersPlusPadding;
 }