Upload/Download dart_snapshotter

mojo/public/dart/rules.gni

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This file has rules for making Dart packages and Dart-based Mojo applications.
 #
 # Entrypoint rules are:
 # - dart_pkg
 # - dartzip_package
 # - dartzip_packaged_application
 
+import("../mojo.gni")
 import("//build/module_args/mojo.gni")
 import("//build/module_args/dart.gni")
 
 template("dartx") {
   bundle_prefix = target_name
   bundle = "$target_gen_dir/${bundle_prefix}.dartx"
   snapshot = "$target_gen_dir/${bundle_prefix}_snapshot.bin"
-  dart_snapshotter = "$root_out_dir/dart_snapshotter"
-  if (current_toolchain != host_toolchain) {
-    toolchain_name = get_label_info(host_toolchain, "name")
-    dart_snapshotter = "$root_out_dir/$toolchain_name/dart_snapshotter"
+
+  if (mojo_use_prebuilt_dart_snapshotter) {
+    dart_snapshotter_path =
+        rebase_path("mojo/public/tools:copy_dart_snapshotter", ".", mojo_root)
+    dart_snapshotter_rule = "$dart_snapshotter_path($host_toolchain)"
+  } else {
+    dart_snapshotter_rule = dart_snapshotter_bin
   }
+  dart_snapshotter_dir =
+      get_label_info("$dart_snapshotter_rule", "root_out_dir")
+  dart_snapshotter = "$dart_snapshotter_dir/dart_snapshotter"
 
   action("gen_${bundle_prefix}_snapshot") {
     main_dart = invoker.main_dart
 
     inputs = [
       dart_snapshotter,
       main_dart,
     ]
     outputs = [
       snapshot,
     ]
 
     if (defined(invoker.sources)) {
       inputs += invoker.sources
     }
 
     script =
         rebase_path("mojo/public/tools/dart_snapshotter.py", ".", mojo_sdk_root)
 
     args = [
       rebase_path(dart_snapshotter),
       rebase_path(main_dart),
       "--package-root",
       rebase_path("$root_gen_dir/dart-pkg/packages"),
       "--snapshot",
       rebase_path(snapshot),
     ]
 
     deps = [
-      dart_snapshotter_bin,
+      dart_snapshotter_rule,
     ]
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
   }
 
   action("gen_${bundle_prefix}_bundle") {
     sources = [
       rebase_path("mojo/public/tools/dartx.py", ".", mojo_sdk_root),
       snapshot,
@@ skipping 534 matching lines @@
 
     rebase_input = rebase_path(input, root_build_dir)
     rebase_output = rebase_path(output, root_build_dir)
     args = [
       "--input=$rebase_input",
       "--output=$rebase_output",
       "--line=$line",
     ]
   }
 }