[fuzzing] Allow resolver fuzzer to specify config vars (#33244)

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test/core/ext/filters/event_engine_client_channel_resolver/BUILD

@@ -26,7 +26,10 @@ grpc_proto_fuzzer(
     corpus = "resolver_fuzzer_corpus",
     language = "C++",
     proto = "resolver_fuzzer.proto",
-    proto_deps = ["//test/core/util:fuzzing_channel_args_proto"],
+    proto_deps = [
+        "//test/core/util:fuzz_config_vars_proto",
+        "//test/core/util:fuzzing_channel_args_proto",
+    ],
     tags = [
         "no_mac",
         "no_windows",
@@ -39,6 +42,7 @@ grpc_proto_fuzzer(
         "//src/core:channel_args",
         "//test/core/event_engine:aborting_event_engine",
         "//test/core/event_engine/fuzzing_event_engine",
+        "//test/core/util:fuzz_config_vars",
         "//test/core/util:fuzzing_channel_args",
         "//test/core/util:grpc_test_util",
         "//test/core/util:grpc_test_util_base",

test/core/ext/filters/event_engine_client_channel_resolver/resolver_fuzzer.cc

@@ -38,6 +38,7 @@
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/event_engine/default_event_engine.h"
 #include "src/core/lib/event_engine/tcp_socket_utils.h"
+#include "src/core/lib/experiments/config.h"
 #include "src/core/lib/gprpp/debug_location.h"
 #include "src/core/lib/gprpp/orphanable.h"
 #include "src/core/lib/gprpp/work_serializer.h"
@@ -49,6 +50,7 @@
 #include "test/core/event_engine/fuzzing_event_engine/fuzzing_event_engine.pb.h"
 #include "test/core/event_engine/util/aborting_event_engine.h"
 #include "test/core/ext/filters/event_engine_client_channel_resolver/resolver_fuzzer.pb.h"
+#include "test/core/util/fuzz_config_vars.h"
 #include "test/core/util/fuzzing_channel_args.h"
 
 bool squelch = true;
@@ -278,6 +280,8 @@ grpc_core::ResolverArgs ConstructResolverArgs(
 DEFINE_PROTO_FUZZER(const event_engine_client_channel_resolver::Msg& msg) {
   if (squelch) gpr_set_log_function(dont_log);
   bool done_resolving = false;
+  grpc_core::ApplyFuzzConfigVars(msg.config_vars());
+  grpc_core::TestOnlyReloadExperimentsFromConfigVariables();
   grpc_event_engine::experimental::SetEventEngineFactory([msg,
                                                           &done_resolving]() {
     return std::make_unique<FuzzingResolverEventEngine>(msg, &done_resolving);

test/core/ext/filters/event_engine_client_channel_resolver/resolver_fuzzer.proto

@@ -17,6 +17,7 @@ syntax = "proto3";
 package event_engine_client_channel_resolver;
 
 import "test/core/util/fuzzing_channel_args.proto";
+import "test/core/util/fuzz_config_vars.proto";
 
 message Error {
     uint32 code = 1;
@@ -72,6 +73,7 @@ enum ExecutionStep {
 
 message Msg {
     grpc.testing.FuzzingChannelArgs channel_args = 1;
+    grpc.testing.FuzzConfigVars config_vars = 9;
     oneof hostname {
         ResolvedAddresses hostname_response = 2;
         Error hostname_error = 3;