Copy build changes to compile mojo::AsyncWaiter to the chromium repo.

mojo/environment/BUILD.gn

Index: mojo/environment/BUILD.gn
diff --git a/mojo/environment/BUILD.gn b/mojo/environment/BUILD.gn
index d08ca6261df6ff5522875024dee06b5ac0a01d62..24df8586a1d08688b7cc1a7fa3358059fb47c551 100644
--- a/mojo/environment/BUILD.gn
+++ b/mojo/environment/BUILD.gn
@@ -10,6 +10,8 @@ source_set("chromium") {
     "environment.cc",
 
     # TODO(vtl): This is kind of ugly. (See TODO in logging.h.)
+    "//third_party/mojo/src/mojo/public/cpp/environment/async_waiter.h",
+    "//third_party/mojo/src/mojo/public/cpp/environment/lib/async_waiter.cc",
     "//third_party/mojo/src/mojo/public/cpp/environment/logging.h",
     "//third_party/mojo/src/mojo/public/cpp/environment/lib/logging.cc",
   ]
@@ -17,6 +19,13 @@ source_set("chromium") {
   public_deps = [
     ":chromium_impl",
   ]
+
+  deps = [
+    "//third_party/mojo/src/mojo/public/c/environment",
+    "//third_party/mojo/src/mojo/public/cpp/bindings:callback",
+    "//third_party/mojo/src/mojo/public/cpp/environment",
+    "//third_party/mojo/src/mojo/public/cpp/system",
+  ]
 }
 
 # GYP version: mojo_base.gyp:mojo_environment_chromium_impl
@@ -35,11 +44,13 @@ component("chromium_impl") {
 
   defines = [ "MOJO_ENVIRONMENT_IMPL_IMPLEMENTATION" ]
 
-  public_configs = [ "//third_party/mojo/src/mojo/public/build/config:mojo_sdk" ]
+  public_configs =
+      [ "//third_party/mojo/src/mojo/public/build/config:mojo_sdk" ]
 
   deps = [
     "//base",
     "//base/third_party/dynamic_annotations",
     "//mojo/common",
+    "//third_party/mojo/src/mojo/public/c/environment",
   ]
 }