[Extensions] Remove JSONFeatureProvider, SimpleFeature::Parse

extensions/common/features/api_feature.cc

Index: extensions/common/features/api_feature.cc
diff --git a/extensions/common/features/api_feature.cc b/extensions/common/features/api_feature.cc
index 20a5f1012c09e00033b551b54ed0e15f2bd334a6..971931b06e4631816dacf682bd729d3ca3d89d20 100644
--- a/extensions/common/features/api_feature.cc
+++ b/extensions/common/features/api_feature.cc
@@ -11,16 +11,4 @@ APIFeature::APIFeature() {}
 APIFeature::~APIFeature() {
 }
 
-bool APIFeature::Validate(std::string* error) {
-  if (!SimpleFeature::Validate(error))
-    return false;
-
-  if (contexts().empty()) {
-    *error = name() + ": API features must specify at least one context.";
-    return false;
-  }
-
-  return true;
-}
-
 }  // namespace extensions