[ddc] Update ddb script for new ddc modules

Add a body tag to the html dart:html can work when running in chrome.

Change-Id: I0d046d8033a734bd610091c52d1410cc72edec84
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/423521
Reviewed-by: Srujan Gaddam <srujzs@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>
diff --git a/pkg/dev_compiler/tool/ddb b/pkg/dev_compiler/tool/ddb
index d21d910..129c1ff 100755
--- a/pkg/dev_compiler/tool/ddb
+++ b/pkg/dev_compiler/tool/ddb
@@ -349,14 +349,19 @@
         for (var output in outputs) '<script src="$output"></script>'
       ].join('\n');
       var ddcModulesHtml = '''
-<script src="$preamblesDir/seal_native_object.js"></script>
-<script src="$ddcPath/lib/js/ddc/ddc_module_loader.js"></script>
-<script src="$sdkJsPath/dart_sdk.js"></script>
-$ddcModuleScriptTags
-<script>
-$ddcModuleSdkOptions
-$ddcModuleRunMain
-</script>
+<html>
+  <head></head>
+  <body>
+    <script src="$preamblesDir/seal_native_object.js"></script>
+    <script src="$ddcPath/lib/js/ddc/ddc_module_loader.js"></script>
+    <script src="$sdkJsPath/dart_sdk.js"></script>
+    $ddcModuleScriptTags
+    <script>
+    $ddcModuleSdkOptions
+    $ddcModuleRunMain
+    </script>
+  </body>
+</html>
 ''';
       var htmlFile = p.setExtension(entryPoint, '.html');
       File(htmlFile)