blink: Add backdrop-filter support

Source/modules/canvas2d/CanvasRenderingContext2DState.h

Index: Source/modules/canvas2d/CanvasRenderingContext2DState.h
diff --git a/Source/modules/canvas2d/CanvasRenderingContext2DState.h b/Source/modules/canvas2d/CanvasRenderingContext2DState.h
index 628f3cd0e7e75721e5dd90291b17dfada4bad97d..485345814bc65d8dc13750917ac6e95842aa7e4d 100644
--- a/Source/modules/canvas2d/CanvasRenderingContext2DState.h
+++ b/Source/modules/canvas2d/CanvasRenderingContext2DState.h
@@ -86,6 +86,12 @@ public:
     SkImageFilter* getFilter(Element*, const Font&) const;
     bool hasFilter() const { return m_filterValue; }
 
+    void setBackdropFilter(PassRefPtrWillBeRawPtr<CSSValue>);
+    void setUnparsedBackdropFilter(const String& filterString) { m_unparsedBackdropFilter = filterString; }
+    const String& unparsedBackdropFilter() const { return m_unparsedBackdropFilter; }
+    SkImageFilter* getBackdropFilter(Element*, const Font&) const;
+    bool hasBackdropFilter() const { return m_backdropFilterValue; }
+
     void setStrokeStyle(CanvasStyle*);
     CanvasStyle* strokeStyle() const { return m_strokeStyle.get(); }
 
@@ -203,6 +209,10 @@ private:
     RefPtrWillBeMember<CSSValue> m_filterValue;
     mutable RefPtr<SkImageFilter> m_resolvedFilter;
 
+    String m_unparsedBackdropFilter;
+    RefPtrWillBeMember<CSSValue> m_backdropFilterValue;
+    mutable RefPtr<SkImageFilter> m_resolvedBackdropFilter;
+
     // Text state.
     TextAlign m_textAlign;
     TextBaseline m_textBaseline;