Adds filter support for offscreen canvas

third_party/WebKit/Source/core/css/CSSToLengthConversionData.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 54 matching lines @@
 {
     ASSERT(m_font);
     return m_font->getFontMetrics().zeroWidth();
 }
 
 CSSToLengthConversionData::ViewportSize::ViewportSize(const LayoutViewItem& layoutViewItem)
     : m_size(!layoutViewItem.isNull() ? layoutViewItem.viewportSizeForViewportUnits() : DoubleSize())
 {
 }
 
+CSSToLengthConversionData::CSSToLengthConversionData(const ComputedStyle* style, float zoom)
+    : m_style(style)
+    , m_zoom(clampTo<float>(zoom, std::numeric_limits<float>::denorm_min()))
+{
+}
+
 CSSToLengthConversionData::CSSToLengthConversionData(const ComputedStyle* style, const FontSizes& fontSizes, const ViewportSize& viewportSize, float zoom)
     : m_style(style)
     , m_fontSizes(fontSizes)
     , m_viewportSize(viewportSize)
     , m_zoom(clampTo<float>(zoom, std::numeric_limits<float>::denorm_min()))
 {
     ASSERT(m_style);
 }
 
 CSSToLengthConversionData::CSSToLengthConversionData(const ComputedStyle* style, const ComputedStyle* rootStyle, const LayoutViewItem& layoutViewItem, float zoom)
@@ skipping 81 matching lines @@
     case CSSPrimitiveValue::UnitType::Chs:
         return value * chFontSize();
 
     default:
         ASSERT_NOT_REACHED();
         return 0;
     }
 }
 
 } // namespace blink