add library-level docs to help with importing

sdk/lib/collection/collection.dart

@@ -4,6 +4,10 @@
 
 /**
  * Classes and utilities that supplement the collection support in dart:core.
+ * 
+ * To use this library in your code:
+ *
+ *     import 'dart:collection';
  */
 library dart.collection;
 

sdk/lib/convert/convert.dart

@@ -11,8 +11,7 @@
  * provides support for implementing converters in a way which makes them easy to
  * chain and to use with streams.
  *
- * The `dart:convert` library works in both web apps and command-line apps.
- * To use it:
+ * To use this library in your code:
  *
  *     import 'dart:convert';
  *

sdk/lib/developer/developer.dart

@@ -8,6 +8,10 @@
 /// as a result of developer feedback. This library is platform dependent and
 /// therefore it has implementations for both dart2js and the Dart VM. Both are
 /// under development and may not support all operations yet.
+/// 
+/// To use this library in your code:
+/// 
+///     import 'dart:developer';
 ///
 library dart.developer;
 

sdk/lib/isolate/isolate.dart

@@ -7,6 +7,10 @@
  * independent workers that are similar to threads
  * but don't share memory,
  * communicating only via messages.
+ * 
+ * To use this library in your code:
+ * 
+ *     import 'dart:isolate';
  */
 library dart.isolate;
 

sdk/lib/math/math.dart

@@ -4,6 +4,10 @@
 
 /**
  * Mathematical constants and functions, plus a random number generator.
+ * 
+ * To use this library in your code:
+ * 
+ *     import 'dart:math';
  */
 library dart.math;
 

sdk/lib/typed_data/typed_data.dart

@@ -4,6 +4,10 @@
 
 /// Lists that efficiently handle fixed sized data
 /// (for example, unsigned 8 byte integers) and SIMD numeric types.
+/// 
+/// To use this library in your code:
+/// 
+///     import 'dart:typed_data';
 library dart.typed_data;
 
 import 'dart:collection';