Ignore style changes on text node flowthread descendants.

Source/core/layout/LayoutMultiColumnFlowThread.cpp

Index: Source/core/layout/LayoutMultiColumnFlowThread.cpp
diff --git a/Source/core/layout/LayoutMultiColumnFlowThread.cpp b/Source/core/layout/LayoutMultiColumnFlowThread.cpp
index 51c0a42890106bbebbbca8f4a0e21e259904a6d8..f7aa2843721f51a5fcd0689c875a99f8b2307873 100644
--- a/Source/core/layout/LayoutMultiColumnFlowThread.cpp
+++ b/Source/core/layout/LayoutMultiColumnFlowThread.cpp
@@ -645,6 +645,13 @@ void LayoutMultiColumnFlowThread::flowThreadDescendantWillBeRemoved(LayoutObject
 void LayoutMultiColumnFlowThread::flowThreadDescendantStyleWillChange(LayoutObject* descendant, StyleDifference diff, const ComputedStyle& newStyle)
 {
     // If an in-flow descendant goes out-of-flow, we may have to remove a column set.
+    if (descendant->isText()) {
+        // Text nodes inherit all properties from the parent node (including non-inheritable

[dsinclair, 2015/05/25 13:42:47]

Is the larger bug here that we inherit non-inheritable properties? Would the
correct fix to be to fix that?

[mstensho (USE GERRIT), 2015/05/25 18:25:13]

I've been thinking that doing something as crazy as text nodes inheriting all
properties from its parent served some important purpose, such as being able to
share the property data, to save memory. But maybe I'm wrong.

OK, let me try fixing that instead. There are some !isText() checks (or actually
!isTextOrSVGChild()) in LayoutObject::containingBlock() (and probably a bunch of
similar things throughout the code) related to this.

+        // ones). We don't care what its 'position' is. In fact, we _must_ ignore it, since the
+        // parent may be the multicol container, and having that accidentally leaked into children
+        // of the multicol is bad.
+        return;
+    }
     if (newStyle.hasOutOfFlowPosition() && !styleRef().hasOutOfFlowPosition())
         flowThreadDescendantWillBeRemoved(descendant);
 }
@@ -652,6 +659,13 @@ void LayoutMultiColumnFlowThread::flowThreadDescendantStyleWillChange(LayoutObje
 void LayoutMultiColumnFlowThread::flowThreadDescendantStyleDidChange(LayoutObject* descendant, StyleDifference diff, const ComputedStyle& oldStyle)
 {
     // If an out-of-flow descendant goes in-flow, we may have to insert a column set.
+    if (descendant->isText()) {
+        // Text nodes inherit all properties from the parent node (including non-inheritable
+        // ones). We don't care what its 'position' is. In fact, we _must_ ignore it, since the
+        // parent may be the multicol container, and having that accidentally leaked into children
+        // of the multicol is bad.
+        return;
+    }
     if (oldStyle.hasOutOfFlowPosition() && !styleRef().hasOutOfFlowPosition())
         flowThreadDescendantWasInserted(descendant);
 }