Fix some problems reported by clang static analyzer

Source/core/rendering/CompositedLayerMapping.cpp

Index: Source/core/rendering/CompositedLayerMapping.cpp
diff --git a/Source/core/rendering/CompositedLayerMapping.cpp b/Source/core/rendering/CompositedLayerMapping.cpp
index 41a76e068d6cf4fd451e8b2fefc37246fef5289c..e073c4c2f38f18d7ec597b931091abead5463f55 100644
--- a/Source/core/rendering/CompositedLayerMapping.cpp
+++ b/Source/core/rendering/CompositedLayerMapping.cpp
@@ -1303,7 +1303,6 @@ bool CompositedLayerMapping::updateSquashingLayers(bool needsSquashingLayers)
             m_squashingLayer = createGraphicsLayer(CompositingReasonOverlap);
             m_squashingLayer->setDrawsContent(true);
             m_squashingLayer->setNeedsDisplay();
-            layersChanged = true;
 
             // FIXME: containment layer needs a new CompositingReason, CompositingReasonOverlap is not appropriate.
             m_squashingContainmentLayer = createGraphicsLayer(CompositingReasonOverlap);
@@ -1318,7 +1317,6 @@ bool CompositedLayerMapping::updateSquashingLayers(bool needsSquashingLayers)
         if (m_squashingLayer) {
             m_squashingLayer->removeFromParent();
             m_squashingLayer = nullptr;
-            layersChanged = true;
             // FIXME: do we need to invalidate something here?
 
             ASSERT(m_squashingContainmentLayer);