Launch nexes from mojo_shell.

shell/BUILD.gn

Index: shell/BUILD.gn
diff --git a/shell/BUILD.gn b/shell/BUILD.gn
index 3f4838a69c0d969768b0be77038b08bb4ece83f6..4387d3afcd4f1c83371f8e59d1eb33c699213b5b 100644
--- a/shell/BUILD.gn
+++ b/shell/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
+import("//mojo/nacl/config.gni")
 import("//mojo/public/mojo.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
@@ -11,6 +12,14 @@ import("//testing/test.gni")
 # inherently components.
 assert(!is_component_build)
 
+config("gate_nacl") {
+  if (mojo_use_nacl) {
+    defines = [ "MOJO_USE_NACL=1" ]
+  } else {
+    defines = [ "MOJO_USE_NACL=0" ]
+  }
+}
+
 group("shell") {
   testonly = true
 
@@ -191,6 +200,20 @@ source_set("lib") {
     "//url",
   ]
 
+  data_deps = []
+
+  configs += [ ":gate_nacl" ]
+  if (mojo_use_nacl) {
+    sources += [
+      "nacl/nacl_service_runner.cc",
+      "nacl/nacl_service_runner.h",
+    ]
+
+    deps += [ "//mojo/nacl:monacl_sel" ]
+
+    data_deps += [ "//native_client/src/untrusted/irt:irt_core(//native_client/build/toolchain/nacl:irt_${cpu_arch})" ]
+  }
+
   if (is_win) {
     deps -= [ "//shell/domain_socket" ]
   }