blink: Add backdrop-filter support

Source/modules/canvas2d/CanvasRenderingContext2D.cpp

Index: Source/modules/canvas2d/CanvasRenderingContext2D.cpp
diff --git a/Source/modules/canvas2d/CanvasRenderingContext2D.cpp b/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
index 4e3e06d2f42195553adec4d946b0c6b8eb677e55..df3a881ba7f81f8a6804b825b0acf515fff440e0 100644
--- a/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
+++ b/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
@@ -663,6 +663,25 @@ void CanvasRenderingContext2D::setFilter(const String& filterString)
     modifiableState().setFilter(filterValue.release());
 }
 
+String CanvasRenderingContext2D::backdropFilter() const
+{
+    return state().unparsedBackdropFilter();
+}
+
+void CanvasRenderingContext2D::setBackdropFilter(const String& backdropFilterString)
+{
+    if (backdropFilterString == state().unparsedBackdropFilter())
+        return;
+
+    RefPtrWillBeRawPtr<CSSValue> backdropFilterValue = CSSParser::parseSingleValue(CSSPropertyBackdropFilter, backdropFilterString, CSSParserContext(HTMLStandardMode, 0));
+
+    if (!backdropFilterValue || backdropFilterValue->isInitialValue() || backdropFilterValue->isInheritedValue())
+        return;
+
+    modifiableState().setUnparsedBackdropFilter(backdropFilterString);
+    modifiableState().setBackdropFilter(backdropFilterValue.release());
+}
+
 PassRefPtrWillBeRawPtr<SVGMatrixTearOff> CanvasRenderingContext2D::currentTransform() const
 {
     return SVGMatrixTearOff::create(state().transform());