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"
+
+  if (mojo_use_prebuilt_dart_snapshotter) {
+    data_deps = [ rebase_path("mojo/public/tools:copy_dart_snapshotter",
+                              ".",
+                              mojo_root) ]
+  }
+
   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"
   }
 
   action("gen_${bundle_prefix}_snapshot") {
     main_dart = invoker.main_dart
 
     inputs = [
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     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",
     ]
   }
 }