Compute the script Uri lazily

runtime/bin/platform_patch.dart

Index: runtime/bin/platform_patch.dart
diff --git a/runtime/bin/platform_patch.dart b/runtime/bin/platform_patch.dart
index f8d117e74e22ac329ab570f87224ab50b6ecdaf9..a634357534ff2359d3de6afd5a58832221374fc0 100644
--- a/runtime/bin/platform_patch.dart
+++ b/runtime/bin/platform_patch.dart
@@ -32,18 +32,22 @@ class _Platform {
   @patch
   static String _packageConfig() => VMLibraryHooks.packageConfigString;
 
+  @patch
+  static Uri _script() => VMLibraryHooks.platformScript;
+
   // This script singleton is written to by the embedder if applicable.
   static void set _nativeScript(String path) {

[zra, 2017/07/24 15:32:48]

In the standalone VM, this setter is called from the embedder. In
Flutter/Fuchsia, VMLibraryHooks.platformScript is set in the builtin library's
_setupHooks().

-    if (path.startsWith('http:') ||
-        path.startsWith('https:') ||
-        path.startsWith('package:') ||
-        path.startsWith('dart:') ||
-        path.startsWith('data:') ||
-        path.startsWith('file:')) {
-      script = Uri.parse(path);
-    } else {
-      script = Uri.base.resolveUri(new Uri.file(path));
-    }
-    VMLibraryHooks.platformScript = script;
+    VMLibraryHooks.platformScript = (() {
+      if (path.startsWith('http:') ||
+          path.startsWith('https:') ||
+          path.startsWith('package:') ||
+          path.startsWith('dart:') ||
+          path.startsWith('data:') ||
+          path.startsWith('file:')) {
+        return Uri.parse(path);
+      } else {
+        return Uri.base.resolveUri(new Uri.file(path));
+      }
+    });
   }
 }