Suppress get_drt/dartium download if an executable is provided via flag

tools/testing/dart/drt_updater.dart

Index: tools/testing/dart/drt_updater.dart
diff --git a/tools/testing/dart/drt_updater.dart b/tools/testing/dart/drt_updater.dart
index 9c3a6d436d03cbcc767796f7b6ad80666f2ab6b8..d7d53e1711848e5a01f6849b77b982c87c135c56 100644
--- a/tools/testing/dart/drt_updater.dart
+++ b/tools/testing/dart/drt_updater.dart
@@ -53,8 +53,13 @@ class _DartiumUpdater {
 _DartiumUpdater _dumpRenderTreeUpdater;
 _DartiumUpdater _dartiumUpdater;
 
-_DartiumUpdater runtimeUpdater(String runtime) {
-  if (runtime == 'drt') {
+_DartiumUpdater runtimeUpdater(Map configuration) {
+  String runtime = configuration['runtime'];
+  if (!configuration.containsKey(runtime) || configuration[runtime] != '') {

[Bill Hesse, 2012/04/30 13:46:10]

This seems totally wrong.  I think configuration['runtime'] always exists, and
it is never the empty string.  I don't see any place where it is changed. 
Shouldn't you be checking
configuration['drt'] instead?

I would think the condition would be just 
if (runtime == 'drt' && configuration['drt'] == null) {
(return updater) }
All valid keys should always be in the configuration, with their default values
- every key has a default.

[vsm, 2012/04/30 14:00:33]

I'm checking what you suggest.  It's runtime the variable ('drt' or 'dartium'),
not 'runtime' the string.

Isn't the default to configuration['drt'] the empty string and not null?

On 2012/04/30 13:46:10, Bill Hesse wrote:

[Bill Hesse, 2012/05/01 08:03:33]

Oh, I see.  That is really tricky, and easy to overlook.

I would either put a comment in,  pointing out that it is not
configuration['runtime'], but configuration[runtime], or I would just add 
&& configuration['drt'] == ''
to the runtime == 'drt' clause, and similarly for the dartium case.  

Also, is the last 
else {
  return null;
}
in line 75 now dead code?


On 2012/04/30 14:00:33, vsm wrote:

+    // Either the runtime executable does not require updating or an
+    // explicit path is provided via --drt or --dartium.
+    return null;
+  } else if (runtime == 'drt') {
     if (_dumpRenderTreeUpdater === null) {
       _dumpRenderTreeUpdater = new _DartiumUpdater('DumpRenderTree',
                                                    'get_drt.py');