Oilpan: fix build after r197938.

Source/core/html/canvas/CanvasRenderingContext2DState.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 
 #include "core/html/canvas/CanvasRenderingContext2DState.h"
 
 #include "core/css/CSSFontSelector.h"
 #include "core/css/resolver/FilterOperationResolver.h"
@@ skipping 158 matching lines @@
     m_font.update(fontSelector);
     // FIXME: We only really need to invalidate the resolved filter if the font
     // update above changed anything and the filter uses font-dependent units.
     m_resolvedFilter.clear();
 }
 
 DEFINE_TRACE(CanvasRenderingContext2DState)
 {
     visitor->trace(m_strokeStyle);
     visitor->trace(m_fillStyle);
+    visitor->trace(m_filterValue);
     CSSFontSelectorClient::trace(visitor);
 }
 
 void CanvasRenderingContext2DState::setLineDashOffset(float offset)
 {
     m_lineDashOffset = offset;
     m_lineDashDirty = true;
 }
 
 void CanvasRenderingContext2DState::setLineDash(const Vector<float>& dash)
@@ skipping 331 matching lines @@
         paint->setLooper(0);
         paint->setImageFilter(shadowAndForegroundImageFilter());
         return paint;
     }
     paint->setLooper(shadowAndForegroundDrawLooper());
     paint->setImageFilter(0);
     return paint;
 }
 
 } // blink