Return scoped_refptr<CSSVariableData> from ValueFromCustomProperty.

In the near future, it will be necessary for ValueForCustomProperty
to return a CSSVariableData which may not be stored elsewhere. This
is because we need to do a "non-destructive" pre-resolve of registered
custom properties that are used before high priority properties are
applied.

R=futhark@chromium.org

Bug: 641877
Change-Id: Idb1ab4ba7aae77187a4fd86877a0246e56fc82a4
Reviewed-on: https://chromium-review.googlesource.com/1235936Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Anders Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592784}

third_party/blink/renderer/core/css/resolver/css_variable_resolver.cc

@@ -66,7 +66,7 @@ bool CSSVariableResolver::ResolveFallback(CSSParserTokenRange range,
   return ResolveTokenRange(range, options, result);
 }
 
-CSSVariableData* CSSVariableResolver::ValueForCustomProperty(
+scoped_refptr<CSSVariableData> CSSVariableResolver::ValueForCustomProperty(
     AtomicString name) {
   if (variables_seen_.Contains(name)) {
     cycle_start_points_.insert(name);
@@ -98,7 +98,7 @@ CSSVariableData* CSSVariableResolver::ValueForCustomProperty(
       name, *variable_data, resolve_urls, unused_cycle_detected);
   if (!registration) {
     inherited_variables_->SetVariable(name, new_variable_data);
-    return new_variable_data.get();
+    return new_variable_data;
   }
 
   const CSSValue* parsed_value = nullptr;
@@ -117,7 +117,7 @@ CSSVariableData* CSSVariableResolver::ValueForCustomProperty(
   }
   if (!new_variable_data)
     return registration->InitialVariableData();
-  return new_variable_data.get();
+  return new_variable_data;
 }
 
 scoped_refptr<CSSVariableData> CSSVariableResolver::ResolveCustomProperty(
@@ -220,7 +220,7 @@ bool CSSVariableResolver::ResolveVariableReference(CSSParserTokenRange range,
     inherited_variables_ = state_.Style()->InheritedVariables();
     non_inherited_variables_ = state_.Style()->NonInheritedVariables();
   }
-  CSSVariableData* variable_data =
+  scoped_refptr<CSSVariableData> variable_data =
       is_env_variable ? ValueForEnvironmentVariable(variable_name)
                       : ValueForCustomProperty(variable_name);
 
@@ -246,7 +246,7 @@ bool CSSVariableResolver::ResolveVariableReference(CSSParserTokenRange range,
   return true;
 }
 
-CSSVariableData* CSSVariableResolver::ValueForEnvironmentVariable(
+scoped_refptr<CSSVariableData> CSSVariableResolver::ValueForEnvironmentVariable(
     const AtomicString& name) {
   // If we are in a User Agent Shadow DOM then we should not record metrics.
   ContainerNode& scope_root = state_.GetTreeScope().RootNode();

third_party/blink/renderer/core/css/resolver/css_variable_resolver.h

@@ -117,10 +117,11 @@ class CORE_EXPORT CSSVariableResolver {
   // These return null if the custom property is invalid.
 
   // Returns the CSSVariableData for an environment variable.
-  CSSVariableData* ValueForEnvironmentVariable(const AtomicString& name);
+  scoped_refptr<CSSVariableData> ValueForEnvironmentVariable(
+      const AtomicString& name);
   // Returns the CSSVariableData for a custom property, resolving and storing it
   // if necessary.
-  CSSVariableData* ValueForCustomProperty(AtomicString name);
+  scoped_refptr<CSSVariableData> ValueForCustomProperty(AtomicString name);
   // Resolves the CSSVariableData from a custom property declaration.
   scoped_refptr<CSSVariableData> ResolveCustomProperty(AtomicString name,
                                                        const CSSVariableData&,