Use Mojo pipes to signal sync IPC events

ipc/BUILD.gn

Index: ipc/BUILD.gn
diff --git a/ipc/BUILD.gn b/ipc/BUILD.gn
index 4d515d7e7a229d1dba95d7b1036a05f3230eb850..c608f0fb4d2d6daf41b7b9dae255e31d6ef6e179 100644
--- a/ipc/BUILD.gn
+++ b/ipc/BUILD.gn
@@ -94,6 +94,8 @@ component("ipc") {
     "message_filter_router.h",
     "message_router.cc",
     "message_router.h",
+    "mojo_event.cc",
+    "mojo_event.h",
     "param_traits_log_macros.h",
     "param_traits_macros.h",
     "param_traits_read_macros.h",
@@ -127,12 +129,14 @@ component("ipc") {
 
   public_deps = [
     ":param_traits",
+    "//mojo/public/cpp/system",
   ]
   deps = [
     "//base",
 
     # TODO(viettrungluu): Needed for base/lazy_instance.h, which is suspect.
     "//base/third_party/dynamic_annotations",
+    "//mojo/public/cpp/bindings",
   ]
 
   if (is_win || is_mac) {
@@ -155,6 +159,20 @@ source_set("param_traits") {
 }
 
 if (!is_ios) {
+  source_set("run_all_unittests") {
+    testonly = true
+
+    sources = [
+      "run_all_unittests.cc",
+    ]
+
+    deps = [
+      "//base",
+      "//base/test:test_support",
+      "//mojo/edk/system",
+    ]
+  }
+
   test("ipc_tests") {
     sources = [
       "attachment_broker_mac_unittest.cc",
@@ -173,7 +191,6 @@ if (!is_ios) {
       "ipc_test_message_generator.cc",
       "ipc_test_message_generator.h",
       "ipc_test_messages.h",
-      "run_all_unittests.cc",
       "sync_socket_unittest.cc",
     ]
 
@@ -196,6 +213,7 @@ if (!is_ios) {
 
     deps = [
       ":ipc",
+      ":run_all_unittests",
       ":test_support",
       "//base",
       "//base:i18n",