Add Dart_Null, Dart_True, and Dart_False.

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
===================================================================
--- runtime/include/dart_api.h	(revision 1035)
+++ runtime/include/dart_api.h	(working copy)
@@ -139,8 +139,6 @@
  * Requires there to be a current isolate.
  */
 DART_EXPORT Dart_Handle Dart_NewPersistentHandle(Dart_Handle object);

[siva, 2011/11/03 21:45:25]

What is the use case for creating a new persistent handle from another
persistent handle?
Seems like clone functionality.

[turnidge, 2011/11/04 00:03:17]

Someone who is passed a Dart_Handle doesn't know whether it is persistent or
not.  Even if they know it is persistent, they don't know what lifetime it will
have.  My thought is that it makes sense to be able to take an arbitrary
Dart_Handle and be able to save it for later.  Does this make sense?

-// TODO(turnidge): This function currently only works when passes a
-// local handle.  Make it work for both local and persistent handles.
 
 /**
  * Deallocates a persistent handle.
@@ -440,6 +438,15 @@
 // --- Objects ----
 
 /**
+ * Returns the null object.
+ *
+ * Requires there to be a current isolate.
+ *
+ * \return A handle to the null object.
+ */
+DART_EXPORT Dart_Handle Dart_Null();
+
+/**
  * Is this object null?
  */
 DART_EXPORT bool Dart_IsNull(Dart_Handle object);
@@ -567,6 +574,24 @@
 // --- Booleans ----
 
 /**
+ * Returns the True object.
+ *
+ * Requires there to be a current isolate.
+ *
+ * \return A handle to the True object.
+ */
+DART_EXPORT Dart_Handle Dart_True();
+
+/**
+ * Returns the False object.
+ *
+ * Requires there to be a current isolate.
+ *
+ * \return A handle to the False object.
+ */
+DART_EXPORT Dart_Handle Dart_False();
+
+/**
  * Is this object a Boolean?
  */
 DART_EXPORT bool Dart_IsBoolean(Dart_Handle object);