Web Animations CSS: Support animation of {text,box,-webkit-box}-shadow and fix blur clamping

Source/core/rendering/style/ShadowData.cpp

Index: Source/core/rendering/style/ShadowData.cpp
diff --git a/Source/core/rendering/style/ShadowData.cpp b/Source/core/rendering/style/ShadowData.cpp
index 56d6610bedc332b49281b1f702e948d7c708bcf0..7f81d909f6bd37d52a1a0ad6f1d6171e2223fff4 100644
--- a/Source/core/rendering/style/ShadowData.cpp
+++ b/Source/core/rendering/style/ShadowData.cpp
@@ -22,6 +22,8 @@
 #include "config.h"
 #include "core/rendering/style/ShadowData.h"
 
+#include "platform/animation/AnimationUtilities.h"
+
 namespace WebCore {
 
 bool ShadowData::operator==(const ShadowData& o) const
@@ -33,4 +35,16 @@ bool ShadowData::operator==(const ShadowData& o) const
         && m_color == o.m_color;
 }
 
+ShadowData ShadowData::blend(const ShadowData& from, double progress) const
+{
+    if (style() != from.style())
+        return *this;
+
+    return ShadowData(WebCore::blend(from.location(), location(), progress),
+        clampTo<int>(WebCore::blend(from.blur(), blur(), progress), 0),
+        WebCore::blend(from.spread(), spread(), progress),
+        style(),
+        WebCore::blend(from.color(), color(), progress));
+}
+
 } // namespace WebCore