jni: clean up several instances of unused jclass refs (#1743)

Signed-off-by: Mike Schore <mike.schore@gmail.com>
Signed-off-by: JP Simard <jp@jpsim.com>

mobile/library/common/jni/jni_interface.cc

@@ -776,8 +776,6 @@ extern "C" JNIEXPORT jlong JNICALL Java_io_envoyproxy_envoymobile_engine_JniLibr
 extern "C" JNIEXPORT jint JNICALL Java_io_envoyproxy_envoymobile_engine_JniLibrary_startStream(
     JNIEnv* env, jclass, jlong stream_handle, jobject j_context, jboolean explicit_flow_control) {
 
-  jclass jcls_JvmCallbackContext = env->GetObjectClass(j_context);
-
   // TODO: To be truly safe we may need stronger guarantees of operation ordering on this ref.
   jobject retained_context = env->NewGlobalRef(j_context);
   envoy_http_callbacks native_callbacks = {jvm_on_response_headers,
@@ -794,7 +792,6 @@ extern "C" JNIEXPORT jint JNICALL Java_io_envoyproxy_envoymobile_engine_JniLibra
   if (result != ENVOY_SUCCESS) {
     env->DeleteGlobalRef(retained_context); // No callbacks are fired and we need to release
   }
-  env->DeleteLocalRef(jcls_JvmCallbackContext);
   return result;
 }
 
@@ -809,7 +806,6 @@ Java_io_envoyproxy_envoymobile_engine_JniLibrary_registerFilterFactory(JNIEnv* e
   // This will need to be updated for https://github.com/lyft/envoy-mobile/issues/332
   jni_log("[Envoy]", "registerFilterFactory");
   jni_log_fmt("[Envoy]", "j_context: %p", j_context);
-  jclass jcls_JvmFilterFactoryContext = env->GetObjectClass(j_context);
   jobject retained_context = env->NewGlobalRef(j_context);
   jni_log_fmt("[Envoy]", "retained_context: %p", retained_context);
   envoy_http_filter* api = (envoy_http_filter*)safe_malloc(sizeof(envoy_http_filter));
@@ -831,7 +827,6 @@ Java_io_envoyproxy_envoymobile_engine_JniLibrary_registerFilterFactory(JNIEnv* e
   api->instance_context = NULL;
 
   envoy_status_t result = register_platform_api(env->GetStringUTFChars(filter_name, nullptr), api);
-  env->DeleteLocalRef(jcls_JvmFilterFactoryContext);
   return result;
 }
 
@@ -932,7 +927,6 @@ Java_io_envoyproxy_envoymobile_engine_JniLibrary_registerStringAccessor(JNIEnv*
 
   // TODO(goaway): The retained_context leaks, but it's tied to the life of the engine.
   // This will need to be updated for https://github.com/lyft/envoy-mobile/issues/332.
-  jclass jcls_JvmStringAccessorContext = env->GetObjectClass(j_context);
   jobject retained_context = env->NewGlobalRef(j_context);
 
   envoy_string_accessor* string_accessor =
@@ -942,7 +936,6 @@ Java_io_envoyproxy_envoymobile_engine_JniLibrary_registerStringAccessor(JNIEnv*
 
   envoy_status_t result =
       register_platform_api(env->GetStringUTFChars(accessor_name, nullptr), string_accessor);
-  env->DeleteLocalRef(jcls_JvmStringAccessorContext);
   return result;
 }