[gn] Fix gyp/gn translation of use_snapshot

gni/isolate.gni

 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/sanitizers/sanitizers.gni")
 import("v8.gni")
 
 declare_args() {
   # Sets the test isolation mode (noop|prepare|check).
   v8_test_isolation_mode = "noop"
@@ skipping 78 matching lines @@
         icu_use_data_file_flag = "1"
       } else {
         icu_use_data_file_flag = "0"
       }
       if (v8_use_external_startup_data) {
         use_external_startup_data = "1"
       } else {
         use_external_startup_data = "0"
       }
       if (v8_use_snapshot) {
-        use_snapshot = "1"
+        use_snapshot = "true"

[Michael Achenbach, 2016/06/07 07:59:28]

"true", really? Yes :/

       } else {
-        use_snapshot = "0"
+        use_snapshot = "false"
       }
 
       # Note, all paths will be rebased in isolate_driver.py to be relative to
       # the isolate file.
       args = [
         v8_test_isolation_mode,
         "--isolated",
         rebase_path("$root_out_dir/$name.isolated", root_build_dir),
         "--isolate",
         rebase_path(invoker.isolate, root_build_dir),
@@ skipping 49 matching lines @@
         ]
       } else {
         args += [
           "--config-variable",
           "msvs_version=0",
         ]
       }
     }
   }
 }