Implement API features for the Extension API feature system

chrome/common/extensions/features/manifest_feature.cc

Index: chrome/common/extensions/features/manifest_feature.cc
diff --git a/chrome/common/extensions/features/manifest_feature.cc b/chrome/common/extensions/features/manifest_feature.cc
index 51d9fd51d5c39746fa52d00b74f5f0b0b3d6a1e5..cd4a53feabb7aafbe4637e2a21939f8a39a375a9 100644
--- a/chrome/common/extensions/features/manifest_feature.cc
+++ b/chrome/common/extensions/features/manifest_feature.cc
@@ -34,4 +34,20 @@ Feature::Availability ManifestFeature::IsAvailableToContext(
   return CreateAvailability(IS_AVAILABLE);
 }
 
+std::string ManifestFeature::Parse(const DictionaryValue* value) {
+  std::string error = SimpleFeature::Parse(value);
+  if (!error.empty())
+    return error;
+
+  if (extension_types()->empty()) {
+    return name() + ": Manifest features must specify at least one " +
+        "value for extension_types.";
+  }
+
+  if (!GetContexts()->empty())
+    return name() + ": Manifest features do not support contexts.";
+
+  return "";
+}
+
 }  // namespace