Dedupe LoadingAttrValue with LoadingAttributeValue.

The TokenPreloadScanner::StartTagScanner class has its own
LoadingAttrValue enum, and member of this type.

However, we've introduced a more general LoadingAttributeValue enum,
along with a helper method to convert strings to members of this enum.

The StartTagScanner class should use these more general primitives,
as opposed to providing its own.
This is good so that the preload scanner infrastructure does not
accidentally become out-of-sync with other code that uses the more
general LoadingAttributeValue class.

Bug: 1099123
Change-Id: I7a07e17baa722881b10bd55ae28d10976bfae50b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2267518Reviewed-by: Dominic Farolino <dom@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Dominic Farolino <dom@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782899}

third_party/blink/renderer/core/html/parser/html_preload_scanner.cc

@@ -47,6 +47,7 @@
 #include "third_party/blink/renderer/core/html/html_image_element.h"
 #include "third_party/blink/renderer/core/html/html_meta_element.h"
 #include "third_party/blink/renderer/core/html/link_rel_attribute.h"
+#include "third_party/blink/renderer/core/html/loading_attribute.h"
 #include "third_party/blink/renderer/core/html/parser/html_parser_idioms.h"
 #include "third_party/blink/renderer/core/html/parser/html_srcset_parser.h"
 #include "third_party/blink/renderer/core/html/parser/html_tokenizer.h"
@@ -150,7 +151,7 @@ class TokenPreloadScanner::StartTagScanner {
         referrer_policy_(network::mojom::ReferrerPolicy::kDefault),
         integrity_attr_set_(false),
         integrity_features_(features),
-        loading_attr_value_(LoadingAttrValue::kAuto),
+        loading_attr_value_(LoadingAttributeValue::kAuto),
         width_attr_dimension_type_(
             HTMLImageElement::LazyLoadDimensionType::kNotAbsolute),
         height_attr_dimension_type_(
@@ -317,8 +318,6 @@ class TokenPreloadScanner::StartTagScanner {
   }
 
  private:
-  enum class LoadingAttrValue { kAuto, kLazy, kEager };
-
   template <typename NameType>
   void ProcessScriptAttribute(const NameType& attribute_name,
                               const String& attribute_value) {
@@ -377,15 +376,10 @@ class TokenPreloadScanner::StartTagScanner {
                Match(attribute_name, html_names::kImportanceAttr) &&
                priority_hints_origin_trial_enabled_) {
       SetImportance(attribute_value);
-    } else if (loading_attr_value_ == LoadingAttrValue::kAuto &&
+    } else if (loading_attr_value_ == LoadingAttributeValue::kAuto &&
                Match(attribute_name, html_names::kLoadingAttr) &&
                RuntimeEnabledFeatures::LazyImageLoadingEnabled()) {
-      loading_attr_value_ =
-          EqualIgnoringASCIICase(attribute_value, "eager")
-              ? LoadingAttrValue::kEager
-              : EqualIgnoringASCIICase(attribute_value, "lazy")
-                    ? LoadingAttrValue::kLazy
-                    : LoadingAttrValue::kAuto;
+      loading_attr_value_ = GetLoadingAttributeValue(attribute_value);
     } else if (width_attr_dimension_type_ ==
                    HTMLImageElement::LazyLoadDimensionType::kNotAbsolute &&
                Match(attribute_name, html_names::kWidthAttr) &&
@@ -553,11 +547,11 @@ class TokenPreloadScanner::StartTagScanner {
     }
 
     switch (loading_attr_value_) {
-      case LoadingAttrValue::kEager:
+      case LoadingAttributeValue::kEager:
         return false;
-      case LoadingAttrValue::kLazy:
+      case LoadingAttributeValue::kLazy:
         return true;
-      case LoadingAttrValue::kAuto:
+      case LoadingAttributeValue::kAuto:
         if ((width_attr_dimension_type_ ==
                  HTMLImageElement::LazyLoadDimensionType::kAbsoluteSmall &&
              height_attr_dimension_type_ ==
@@ -751,7 +745,7 @@ class TokenPreloadScanner::StartTagScanner {
   bool integrity_attr_set_;
   IntegrityMetadataSet integrity_metadata_;
   SubresourceIntegrity::IntegrityFeatures integrity_features_;
-  LoadingAttrValue loading_attr_value_;
+  LoadingAttributeValue loading_attr_value_;
   HTMLImageElement::LazyLoadDimensionType width_attr_dimension_type_;
   HTMLImageElement::LazyLoadDimensionType height_attr_dimension_type_;
   HTMLImageElement::LazyLoadDimensionType inline_style_dimensions_type_;