Merge r139337 to M25.

Source/WebCore/ChangeLog

Index: Source/WebCore/ChangeLog
===================================================================
--- Source/WebCore/ChangeLog	(revision 140446)
+++ Source/WebCore/ChangeLog	(working copy)
@@ -1,3 +1,19 @@
+2013-01-10  Robert Hogan  <robert@webkit.org>
+
+        REGRESSION(r136967): margin-top + overflow:hidden causes incorrect layout for internal floated elements
+        https://bugs.webkit.org/show_bug.cgi?id=106374
+
+        Reviewed by David Hyatt.
+
+        r136397 treated any self-collapsing block that had a clearance delta as though it was clearing a float, but
+        blocks that avoid floats can get a clearance delta too. So just ensure there is clearance on the block when deciding
+        whether we need to add the margin back in before placing the float.
+
+        Test: fast/block/margin-collapse/self-collapsing-block-with-overflow-hidden-and-float-child.html
+
+        * rendering/RenderBlockLineLayout.cpp:
+        (WebCore::RenderBlock::LineBreaker::skipLeadingWhitespace):
+
 2013-01-09  Tien-Ren Chen  <trchen@chromium.org>
 
         Make caret repainting container-aware