Implement DeclarationMirror.location for all but ParameterMirrors.

sdk/lib/mirrors/mirrors.dart

Index: sdk/lib/mirrors/mirrors.dart
diff --git a/sdk/lib/mirrors/mirrors.dart b/sdk/lib/mirrors/mirrors.dart
index d16e62eecb7fc4e63e4518e7ffd4398b8c562fda..224e8799638de4577ff37fcb4880296fb352485e 100644
--- a/sdk/lib/mirrors/mirrors.dart
+++ b/sdk/lib/mirrors/mirrors.dart
@@ -286,9 +286,35 @@ abstract class DeclarationMirror implements Mirror {
   bool get isTopLevel;
 
   /**
-   * The source location of this Dart language entity.
+   * The source location of this Dart language entity, or [:null:] if the
+   * entity is synthetic.
    *
-   * This operation is optional and may return [:null:].
+   * If the reflectee is a variable, the returned location gives the position of   * the variable name at its point of declaration.
+   *
+   * If the reflectee is a library, class, typedef, function or type variable
+   * with associated metadata, the returned location gives the position of the
+   * first metadata declaration associated with the reflectee.
+   *
+   * Otherwise:
+   * If the reflectee is a library, the returned location gives the position of
+   * the keyword 'library' at the reflectee's point of declaration, if the
+   * reflectee is a named library, or the first character of the first line in
+   * the compilation unit defining the reflectee if the reflectee is anonymous.
+   *
+   * If the reflectee is an abstract class, the returned location gives the
+   * position of the keyword 'abstract' at the reflectee's point of declaration.   * Otherwise, if the reflectee is a class, the returned location gives the
+   * position of the keyword 'class' at the reflectee's point of declaration.
+   *
+   * If the reflectee is a typedef the returned location gives the position of
+   * the of the keyword 'typedef' at the reflectee's point of declaration.
+   *
+   * If the reflectee is a function with a declared return type, the returned
+   * location gives the position of the function's return type at the
+   * reflectee's point of declaration. Otherwise. the returned location gives
+   * the position of the function's name at the reflectee's point of
+   * declaration.
+   *
+   * This operation is optional and may throw an [UnsupportedError].
    */
   SourceLocation get location;