Consistently check if a block can handle pagination strut propagation.

third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp

Index: third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp b/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
index 73f871ac2150440e2ac332a2bf69cdc872a8ffe3..bdfb1263371a1844b8acd98918b47bcd82c6aecd 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
@@ -705,7 +705,7 @@ LayoutUnit LayoutBlockFlow::adjustBlockChildForPagination(LayoutUnit logicalTop,
     if (paginationStrut) {
         // We are willing to propagate out to our parent block as long as we were at the top of the block prior
         // to collapsing our margins, and as long as we didn't clear or move as a result of other pagination.
-        if (atBeforeSideOfBlock && logicalTop == newLogicalTop && !isOutOfFlowPositioned() && !isTableCell()) {
+        if (atBeforeSideOfBlock && logicalTop == newLogicalTop && allowsPaginationStrut()) {
             // FIXME: Should really check if we're exceeding the page height before propagating the strut, but we don't
             // have all the information to do so (the strut only has the remaining amount to push). Gecko gets this wrong too
             // and pushes to the next page anyway, so not too concerned about it.
@@ -781,16 +781,7 @@ static inline bool shouldSetStrutOnBlock(const LayoutBlockFlow& block, const Roo
         if (totalLogicalHeight < pageLogicalHeightAtNewOffset)
             wantsStrutOnBlock = true;
     }
-    // The block needs to be contained by a LayoutBlockFlow (and not by e.g. a flexbox or a table
-    // (which would be the case for table cell or table caption)). The reason for this limitation is
-    // simply that LayoutBlockFlow child layout code is the only place where we pick up the struts
-    // and handle them. We handle floats and regular in-flow children, and that's all. We could
-    // handle this in other layout modes as well (and even for out-of-flow children), but currently
-    // we don't.
-    if (!wantsStrutOnBlock || block.isOutOfFlowPositioned())
-        return false;
-    LayoutBlock* containingBlock = block.containingBlock();
-    return containingBlock && containingBlock->isLayoutBlockFlow();
+    return wantsStrutOnBlock && block.allowsPaginationStrut();
 }
 
 void LayoutBlockFlow::adjustLinePositionForPagination(RootInlineBox& lineBox, LayoutUnit& delta)
@@ -2909,6 +2900,20 @@ void LayoutBlockFlow::getSelectionGapInfo(SelectionState state, bool& leftGap, b
         || (state == SelectionEnd && !ltr);
 }
 
+bool LayoutBlockFlow::allowsPaginationStrut() const
+{
+    // The block needs to be contained by a LayoutBlockFlow (and not by e.g. a flexbox or a table
+    // (which would be the case for table cell or table caption)). The reason for this limitation is

[Julien - ping for review, 2015/10/05 17:33:05]

or a grid

[mstensho (USE GERRIT), 2015/10/05 19:51:32]

Done.

+    // simply that LayoutBlockFlow child layout code is the only place where we pick up the struts
+    // and handle them. We handle floats and regular in-flow children, and that's all. We could
+    // handle this in other layout modes as well (and even for out-of-flow children), but currently
+    // we don't.

[Julien - ping for review, 2015/10/05 17:33:05]

TODO(mstensho)?

[mstensho (USE GERRIT), 2015/10/05 19:51:32]

Done.

+    if (isOutOfFlowPositioned())
+        return false;
+    LayoutBlock* containingBlock = this->containingBlock();
+    return containingBlock && containingBlock->isLayoutBlockFlow();
+}
+
 void LayoutBlockFlow::setPaginationStrut(LayoutUnit strut)
 {
     if (!m_rareData) {