- Implement a first cut for const String.env in the VM to allow

sdk/lib/core/string.dart

Index: sdk/lib/core/string.dart
===================================================================
--- sdk/lib/core/string.dart	(revision 27984)
+++ sdk/lib/core/string.dart	(working copy)
@@ -125,6 +125,12 @@
   }
 
   /**
+   * Returns the string for the given environment variable [name] or

[Ivan Posva, 2013/09/27 07:21:01]

Maybe it should say "for the given configuration variable"?

[kasperl, 2013/09/27 07:32:43]

Nit: I don't think we should limit ourselves to environment variables. Also I'd
prefer a non-abbreviated name for this.

Ideally, the variables you can refer to can be defined by the embedder so we can
have them put in script tags in Dartium or passed on the command line for the
standalone VM and dart2js.

[Ivan Posva, 2013/09/27 21:05:06]

That is why had the remark about changing the comment. What we need to decide is
what we call this feature. When I initially wrote this patch in March, the plan
was to call this configuration. Any suggestions as far as naming goes are
appreciated.

I'll continue with env until we settled on a better plan. The other suggestion
the reviews namely "fromEnvironment" is also too specific.

+   * [defaultValue] if [name] is not present.
+   */
+  external const String.env(String name, String defaultValue);

[bakster, 2013/09/27 07:44:39]

How about adding a default value to defaultValue?
  external const String.env(String name, [String defaultValue=''] );

[Ivan Posva, 2013/09/27 21:05:06]

I was thinking the same thing, but instead I would leave the defaults null,
allowing the program to figure out whether a value had been specified or not:

external const String.env(String name, {String default = null});

+
+  /**
    * Gets the character (as a single-code-unit [String]) at the given [index].
    *
    * The returned string represents exactly one UTF-16 code unit, which may be