WIP Support var() references in registered custom property keyframes

third_party/WebKit/Source/core/css/resolver/CSSVariableResolver.cpp

Index: third_party/WebKit/Source/core/css/resolver/CSSVariableResolver.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/CSSVariableResolver.cpp b/third_party/WebKit/Source/core/css/resolver/CSSVariableResolver.cpp
index 46ca6234c121452cf09e72bbed7f34487015a9ed..ade766d04b9c977bb6949bbb3251d3899a0b141f 100644
--- a/third_party/WebKit/Source/core/css/resolver/CSSVariableResolver.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/CSSVariableResolver.cpp
@@ -8,6 +8,7 @@
 #include "core/CSSValueKeywords.h"
 #include "core/StyleBuilderFunctions.h"
 #include "core/StylePropertyShorthand.h"
+#include "core/css/CSSCustomPropertyDeclaration.h"
 #include "core/css/CSSPendingSubstitutionValue.h"
 #include "core/css/CSSUnsetValue.h"
 #include "core/css/CSSVariableData.h"
@@ -100,6 +101,7 @@ PassRefPtr<CSSVariableData> CSSVariableResolver::ResolveCustomProperty(
   Vector<CSSParserToken> tokens;
   Vector<String> backing_strings;
   backing_strings.AppendVector(variable_data.BackingStrings());
+  DCHECK(!variables_seen_.Contains(name));
   variables_seen_.insert(name);
   bool success =
       ResolveTokenRange(variable_data.Tokens(), disallow_animation_tainted,
@@ -126,6 +128,20 @@ bool CSSVariableResolver::ResolveVariableReference(
       range.ConsumeIncludingWhitespace().Value().ToAtomicString();
   DCHECK(range.AtEnd() || (range.Peek().GetType() == kCommaToken));
 
+  PropertyHandle property(variable_name);
+  if (state_.AnimationPendingCustomProperties().Contains(property) &&
+      !variables_seen_.Contains(variable_name)) {
+    // We make the StyleResolverState mutable for animated custom properties as
+    // an optimisation. Without this we would need to compute animated values on
+    // the stack without saving the result or perform an expensive and complex
+    // value dependency graph analysis to compute them in the required order.
+    StyleResolver::ApplyAnimatedCustomProperty(
+        const_cast<StyleResolverState&>(state_), *this, property);
+    // Null custom property storage may become non-null after application, we
+    // must refresh these cached values.
+    inherited_variables_ = state_.Style()->InheritedVariables();
+    non_inherited_variables_ = state_.Style()->NonInheritedVariables();
+  }
   CSSVariableData* variable_data = ValueForCustomProperty(variable_name);
   if (!variable_data ||
       (disallow_animation_tainted && variable_data->IsAnimationTainted())) {
@@ -283,6 +299,31 @@ const CSSValue* CSSVariableResolver::ResolvePendingSubstitutions(
   return CSSUnsetValue::Create();
 }
 
+const CSSValue*
+CSSVariableResolver::ResolveRegisteredCustomPropertyAnimationKeyframe(
+    const PropertyRegistration& registration,
+    const CSSCustomPropertyDeclaration& keyframe) {
+  DCHECK(keyframe.Value());
+  const AtomicString& name = keyframe.GetName();
+  DCHECK_EQ(registry_->Registration(name), &registration);
+
+  if (variables_seen_.Contains(name)) {
+    cycle_start_points_.insert(name);
+    return nullptr;
+  }
+
+  if (!keyframe.Value()->NeedsVariableResolution()) {
+    return keyframe.Value()->ParseForSyntax(registration.Syntax());
+  }
+
+  RefPtr<CSSVariableData> resolved_tokens =
+      ResolveCustomProperty(name, *keyframe.Value());
+  if (!resolved_tokens) {
+    return nullptr;
+  }
+  return resolved_tokens->ParseForSyntax(registration.Syntax());
+}
+
 void CSSVariableResolver::ResolveVariableDefinitions() {
   if (!inherited_variables_ && !non_inherited_variables_)
     return;