BR styled clear is ignored while partially relayouting.

Source/core/layout/LayoutBlockFlowLine.cpp

Index: Source/core/layout/LayoutBlockFlowLine.cpp
diff --git a/Source/core/layout/LayoutBlockFlowLine.cpp b/Source/core/layout/LayoutBlockFlowLine.cpp
index c54361d8dcafb16f8b0377802827645f70be5b36..6011d18a6f7d6927fea45e27c15a110e7afaf2b4 100644
--- a/Source/core/layout/LayoutBlockFlowLine.cpp
+++ b/Source/core/layout/LayoutBlockFlowLine.cpp
@@ -796,7 +796,9 @@ void LayoutBlockFlow::layoutRunsAndFloatsInRange(LineLayoutState& layoutState,
     bool paginated = view()->layoutState() && view()->layoutState()->isPaginated();
     LineMidpointState& lineMidpointState = resolver.midpointState();
     InlineIterator endOfLine = resolver.position();
-    bool checkForEndLineMatch = layoutState.endLine();
+    const bool needsToCheckEndLine = containsFloats() && lastChild() && lastChild()->isBR() && lastChild()->style()->clear();

[leviw_travelin_and_unemployed, 2015/04/24 18:55:47]

Driveby: This needs a better name. The addition of "needs" to the variable
doesn't make it clear what the difference between this and the bool below is.

Why are you checking lastChild directly? Does this only happen when the br in
question is the last child? That seems suspicious...

[changseok, 2015/04/24 21:53:08]

Yes it does as long as I know. If the br places in middle line of
LayoutBlockFlow and something visible like inlineBox or layoutBlock is followed,
then we can determine a endLine with the visible one. This bug only happens when
br with clear is the last child in LayoutBlockFlow. In this case, the end line
is the text node which is just before the last br and the start line is the
anchor. We calculate height with only those two lines so the height shrinks
after re-layout.
However we go over the two line and see the next line, br, we call clearFloats()
in the while loop and then we would finally have correct height of
layoutBlockFlow.

+    bool checkForEndLineMatch = layoutState.endLine() && !needsToCheckEndLine;
+
     LayoutTextInfo renderTextInfo;
     VerticalPositionCache verticalPositionCache;