Add use counters for function values of easing

third_party/WebKit/Source/core/animation/AnimationInputHelpers.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/animation/AnimationInputHelpers.h"
 
 #include "core/SVGNames.h"
 #include "core/css/CSSValueList.h"
 #include "core/css/parser/CSSParser.h"
 #include "core/css/resolver/CSSToStyleMap.h"
@@ skipping 184 matching lines @@
     String unprefixedProperty = removeSVGPrefix(property);
     QualifiedName attributeName = svgAttributeName(unprefixedProperty);
     const AttributeNameMap& supportedAttributes = getSupportedAttributes();
     auto iter = supportedAttributes.find(attributeName);
     if (iter == supportedAttributes.end() || !svgElement.propertyFromAttribute(*iter->value))
         return nullptr;
 
     return iter->value;
 }
 
-PassRefPtr<TimingFunction> AnimationInputHelpers::parseTimingFunction(const String& string)
+PassRefPtr<TimingFunction> AnimationInputHelpers::parseTimingFunction(const String& string, Document* document)
 {
     if (string.isEmpty())
         return nullptr;
 
     CSSValue* value = CSSParser::parseSingleValue(CSSPropertyTransitionTimingFunction, string);
     if (!value || !value->isValueList()) {
         ASSERT(!value || value->isCSSWideKeyword());
+        if (document) {
+            if (string.startsWith("function")) {
+                // Due to a bug in old versions of the web-animations-next
+                // polyfill, in some circumstances the string passed in here
+                // may be a Javascript function instead of the allowed values
+                // from the spec
+                // (http://w3c.github.io/web-animations/#dom-animationeffecttimingreadonly-easing)
+                // This bug was fixed in
+                // https://github.com/web-animations/web-animations-next/pull/423
+                // and we want to track how often it is still being hit. The
+                // linear case is special because 'linear' is the default value
+                // for easing.
+                if (string == "function (a){return a}")
+                    UseCounter::count(*document, UseCounter::WebAnimationsEasingAsFunctionLinear);
+                else
+                    UseCounter::count(*document, UseCounter::WebAnimationsEasingAsFunctionOther);
+            }
+        }
         return nullptr;
     }
     CSSValueList* valueList = toCSSValueList(value);
     if (valueList->length() > 1)
         return nullptr;
     return CSSToStyleMap::mapAnimationTimingFunction(*valueList->item(0), true);
 }
 
 } // namespace blink