Ship dart2js output for dev_compiler/web in the sdk.

sdk/BUILD.gn

Index: sdk/BUILD.gn
diff --git a/sdk/BUILD.gn b/sdk/BUILD.gn
index 0f7d34ca83cb781686eff17473786bd1d1ceb1c3..e0b41bdc2f737ba081007561d3dbe1c502787ab1 100644
--- a/sdk/BUILD.gn
+++ b/sdk/BUILD.gn
@@ -387,4 +387,20 @@ if (defined(is_fuchsia) && (is_fuchsia || is_fuchsia_host)) {
       rebase_path("$root_gen_dir"),
     ]
   }
+
+  copy("copy_dev_compiler_tools") {
+    deps = [
+      ":create_sdk",
+      "../utils/dartdevc:dartdevc_web",
+      "../utils/dartdevc:stack_trace_mapper",
+    ]
+    dart_out = get_label_info("../utils/dartdevc:dartdevc_web", "root_out_dir")
+    sources = [
+      "$dart_out/dev_compiler/build/web/ddc_web_compiler.js",
+      "$dart_out/dev_compiler/build/web/dart_stack_trace_mapper.js",
+    ]
+    outputs = [
+      "$root_out_dir/dart-sdk/lib/dev_compiler/web/{{source_file_part}}",
+    ]
+  }
 }