blink: Add backdrop-filter support

Source/core/animation/DeferredLegacyStyleInterpolationTest.cpp

Index: Source/core/animation/DeferredLegacyStyleInterpolationTest.cpp
diff --git a/Source/core/animation/DeferredLegacyStyleInterpolationTest.cpp b/Source/core/animation/DeferredLegacyStyleInterpolationTest.cpp
index 612908bb64a2c67a72fb2c3b49b61597ffd6c2ec..53218feaea7083d02b9c280052f82ee71dab2025 100644
--- a/Source/core/animation/DeferredLegacyStyleInterpolationTest.cpp
+++ b/Source/core/animation/DeferredLegacyStyleInterpolationTest.cpp
@@ -90,4 +90,20 @@ TEST_F(AnimationDeferredLegacyStyleInterpolationTest, Filter)
     EXPECT_TRUE(test(CSSPropertyWebkitFilter, "url(#svgfilter)"));
 }
 
+TEST_F(AnimationDeferredLegacyStyleInterpolationTest, BackdropFilter)
+{
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "hue-rotate(180deg) blur(6px)"));
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "grayscale(0) blur(0px)"));
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "none"));
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "brightness(0) contrast(0)"));
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "drop-shadow(20px 10px green)"));
+    EXPECT_TRUE(test(CSSPropertyBackdropFilter, "drop-shadow(20px 10vw green)"));
+    EXPECT_TRUE(test(CSSPropertyBackdropFilter, "drop-shadow(0px 0px 0px currentcolor)"));
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "opacity(1)"));
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "saturate(0)"));
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "grayscale(1)"));
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "invert(1)"));
+    EXPECT_FALSE(test(CSSPropertyBackdropFilter, "sepia(1)"));
+    EXPECT_TRUE(test(CSSPropertyBackdropFilter, "url(#svgfilter)"));
+}
 }