[New Multicolumn] Support for block direction margins on spanners.

Source/core/rendering/RenderMultiColumnSpannerPlaceholder.cpp

Index: Source/core/rendering/RenderMultiColumnSpannerPlaceholder.cpp
diff --git a/Source/core/rendering/RenderMultiColumnSpannerPlaceholder.cpp b/Source/core/rendering/RenderMultiColumnSpannerPlaceholder.cpp
index b0555a5b2af6c9766a4a282382d2e39e16ee7c6e..f028dcf4b871ce38e4399eadaad1ad898b759ece 100644
--- a/Source/core/rendering/RenderMultiColumnSpannerPlaceholder.cpp
+++ b/Source/core/rendering/RenderMultiColumnSpannerPlaceholder.cpp
@@ -7,12 +7,23 @@
 
 namespace blink {
 
+static void copyMarginProperties(RenderStyle* placeholderStyle, const RenderStyle* spannerStyle)
+{
+    // We really only need the block direction margins, but there are no setters for that in
+    // RenderStyle. Just copy all margin sides. The inline ones don't matter anyway.
+    placeholderStyle->setMarginLeft(spannerStyle->marginLeft());
+    placeholderStyle->setMarginRight(spannerStyle->marginRight());
+    placeholderStyle->setMarginTop(spannerStyle->marginTop());
+    placeholderStyle->setMarginBottom(spannerStyle->marginBottom());
+}
+
 RenderMultiColumnSpannerPlaceholder* RenderMultiColumnSpannerPlaceholder::createAnonymous(RenderStyle* parentStyle, RenderBox* rendererInFlowThread)
 {
     RenderMultiColumnSpannerPlaceholder* newSpanner = new RenderMultiColumnSpannerPlaceholder(rendererInFlowThread);
     Document& document = rendererInFlowThread->document();
     newSpanner->setDocumentForAnonymous(&document);
     RefPtr<RenderStyle> newStyle = RenderStyle::createAnonymousStyleWithDisplay(parentStyle, BLOCK);
+    copyMarginProperties(newStyle.get(), rendererInFlowThread->style());
     newSpanner->setStyle(newStyle);
     return newSpanner;
 }
@@ -32,6 +43,13 @@ void RenderMultiColumnSpannerPlaceholder::spannerWillBeRemoved()
     // |this| should be destroyed by now.
 }
 
+void RenderMultiColumnSpannerPlaceholder::updateMarginProperties()
+{
+    RefPtr<RenderStyle> newStyle = RenderStyle::clone(style());
+    copyMarginProperties(newStyle.get(), m_rendererInFlowThread->style());
+    setStyle(newStyle);

[Julien - ping for review, 2015/01/20 08:55:15]

Won't this trigger another run through styleWillChange / styleDidChange?

[mstensho (USE GERRIT), 2015/01/20 09:23:30]

Yeah, but on this object, not on the RenderBox that has column-span:all.

[Julien - ping for review, 2015/01/20 16:52:45]

Morten made me realize on IRC that we can't skip the setStyle. This is how the
style is propagated to anonymous renderers and it's the only safe way to do it.

+}
+
 void RenderMultiColumnSpannerPlaceholder::willBeRemovedFromTree()
 {
     if (m_rendererInFlowThread)
@@ -62,6 +80,8 @@ void RenderMultiColumnSpannerPlaceholder::computeLogicalHeight(LayoutUnit, Layou
 {
     computedValues.m_extent = m_rendererInFlowThread->logicalHeight();
     computedValues.m_position = logicalTop;
+    computedValues.m_margins.m_before = marginBefore();
+    computedValues.m_margins.m_after = marginAfter();
 }
 
 void RenderMultiColumnSpannerPlaceholder::invalidateTreeIfNeeded(const PaintInvalidationState& paintInvalidationState)