Adds filter support for offscreen canvas

third_party/WebKit/Source/core/css/resolver/StyleResolverState.h

Index: third_party/WebKit/Source/core/css/resolver/StyleResolverState.h
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleResolverState.h b/third_party/WebKit/Source/core/css/resolver/StyleResolverState.h
index 912098578eab311099bae194f3156b6e491747f2..6e0304667d769afbbc740d973709620b5f354937 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleResolverState.h
+++ b/third_party/WebKit/Source/core/css/resolver/StyleResolverState.h
@@ -47,12 +47,14 @@ class CORE_EXPORT StyleResolverState {
     STACK_ALLOCATED();
     WTF_MAKE_NONCOPYABLE(StyleResolverState);
 public:
+    StyleResolverState(const ComputedStyle* parentStyle);
     StyleResolverState(Document&, const ElementResolveContext&, const ComputedStyle* parentStyle);
     StyleResolverState(Document&, Element*, const ComputedStyle* parentStyle = 0);
     ~StyleResolverState();
 
     // In FontFaceSet and CanvasRenderingContext2D, we don't have an element to grab the document from.
     // This is why we have to store the document separately.
+    bool hasDocument() const { return m_document; }
     Document& document() const { return *m_document; }
     // These are all just pass-through methods to ElementResolveContext.
     Element* element() const { return m_elementContext.element(); }
@@ -67,7 +69,11 @@ public:
     {
         // FIXME: Improve RAII of StyleResolverState to remove this function.
         m_style = style;
-        m_cssToLengthConversionData = CSSToLengthConversionData(m_style.get(), rootElementStyle(), document().layoutViewItem(), m_style->effectiveZoom());
+        if (m_document) {
+            m_cssToLengthConversionData = CSSToLengthConversionData(m_style.get(), rootElementStyle(), document().layoutViewItem(), m_style->effectiveZoom());
+        } else {
+            m_cssToLengthConversionData = CSSToLengthConversionData(m_style.get(), m_style->effectiveZoom());
+        }
     }
     const ComputedStyle* style() const { return m_style.get(); }
     ComputedStyle* style() { return m_style.get(); }