Decouple filter selection from channel construction

Allow plugins to extend the set of filters used by gRPC core:
- plugins at construction time can register against the 'channel_init' system to be allowed to mutate a new channel_stack_builder type
- channel_stack_builder provides a central and rather dynamic place to construct the list of filters required by a channel stack
- ultimately we construct the channel stack in the fashion we always have

This is also a prerequisite step to allowing filters to be implemented from wrapped languages.
diff --git a/test/core/end2end/fixtures/h2_full+trace.c b/test/core/end2end/fixtures/h2_full+trace.c
new file mode 100644
index 0000000..3988ca0
--- /dev/null
+++ b/test/core/end2end/fixtures/h2_full+trace.c
@@ -0,0 +1,132 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "test/core/end2end/end2end_tests.h"
+
+#include <string.h>
+
+#include "src/core/channel/client_channel.h"
+#include "src/core/channel/connected_channel.h"
+#include "src/core/channel/http_server_filter.h"
+#include "src/core/surface/channel.h"
+#include "src/core/surface/server.h"
+#include "src/core/transport/chttp2_transport.h"
+#include <grpc/support/alloc.h>
+#include <grpc/support/host_port.h>
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/thd.h>
+#include <grpc/support/useful.h>
+#include "test/core/util/port.h"
+#include "test/core/util/test_config.h"
+#include "src/core/support/env.h"
+
+typedef struct fullstack_fixture_data {
+  char *localaddr;
+} fullstack_fixture_data;
+
+static grpc_end2end_test_fixture chttp2_create_fixture_fullstack(
+    grpc_channel_args *client_args, grpc_channel_args *server_args) {
+  grpc_end2end_test_fixture f;
+  int port = grpc_pick_unused_port_or_die();
+  fullstack_fixture_data *ffd = gpr_malloc(sizeof(fullstack_fixture_data));
+  memset(&f, 0, sizeof(f));
+
+  gpr_join_host_port(&ffd->localaddr, "localhost", port);
+
+  f.fixture_data = ffd;
+  f.cq = grpc_completion_queue_create(NULL);
+
+  return f;
+}
+
+void chttp2_init_client_fullstack(grpc_end2end_test_fixture *f,
+                                  grpc_channel_args *client_args) {
+  fullstack_fixture_data *ffd = f->fixture_data;
+  f->client = grpc_insecure_channel_create(ffd->localaddr, client_args, NULL);
+  GPR_ASSERT(f->client);
+}
+
+void chttp2_init_server_fullstack(grpc_end2end_test_fixture *f,
+                                  grpc_channel_args *server_args) {
+  fullstack_fixture_data *ffd = f->fixture_data;
+  if (f->server) {
+    grpc_server_destroy(f->server);
+  }
+  f->server = grpc_server_create(server_args, NULL);
+  grpc_server_register_completion_queue(f->server, f->cq, NULL);
+  GPR_ASSERT(grpc_server_add_insecure_http2_port(f->server, ffd->localaddr));
+  grpc_server_start(f->server);
+}
+
+void chttp2_tear_down_fullstack(grpc_end2end_test_fixture *f) {
+  fullstack_fixture_data *ffd = f->fixture_data;
+  gpr_free(ffd->localaddr);
+  gpr_free(ffd);
+}
+
+/* All test configurations */
+static grpc_end2end_test_config configs[] = {
+    {"chttp2/fullstack", FEATURE_MASK_SUPPORTS_DELAYED_CONNECTION,
+     chttp2_create_fixture_fullstack, chttp2_init_client_fullstack,
+     chttp2_init_server_fullstack, chttp2_tear_down_fullstack},
+};
+
+int main(int argc, char **argv) {
+  size_t i;
+
+  /* force tracing on, with a value to force many
+     code paths in trace.c to be taken */
+  gpr_setenv("GRPC_TRACE", "doesnt-exist,http,all");
+
+#ifdef GPR_POSIX_SOCKET
+  g_fixture_slowdown_factor = isatty(STDOUT_FILENO) ? 10.0 : 1.0;
+#else
+  g_fixture_slowdown_factor = 10.0;
+#endif
+
+  grpc_test_init(argc, argv);
+  grpc_init();
+
+  for (i = 0; i < sizeof(configs) / sizeof(*configs); i++) {
+    grpc_end2end_tests(argc, argv, configs[i]);
+  }
+
+  GPR_ASSERT(0 == grpc_tracer_set_enabled("also-doesnt-exist", 0));
+  GPR_ASSERT(1 == grpc_tracer_set_enabled("http", 1));
+  GPR_ASSERT(1 == grpc_tracer_set_enabled("all", 1));
+
+  grpc_shutdown();
+
+  return 0;
+}