Access to imports in the VM's runtime mirrors. Extend test coverage of the source mirrors.

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 1c66c5af8848b357d9e7ac223d6b655dd0b50a66..b4dfc4e8f2ec2016403a59243038390a70766026 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -2621,6 +2621,8 @@ class Library : public Object {
   RawArray* anonymous_classes() const { return raw_ptr()->anonymous_classes_; }
 
   // Library imports.
+  RawArray* imports() const { return raw_ptr()->imports_; }
+  RawArray* exports() const { return raw_ptr()->exports_; }
   void AddImport(const Namespace& ns) const;
   intptr_t num_imports() const { return raw_ptr()->num_imports_; }
   RawNamespace* ImportAt(intptr_t index) const;
@@ -2706,8 +2708,6 @@ class Library : public Object {
   void set_num_imports(intptr_t value) const {
     raw_ptr()->num_imports_ = value;
   }
-  RawArray* imports() const { return raw_ptr()->imports_; }
-  RawArray* exports() const { return raw_ptr()->exports_; }
   bool HasExports() const;
   RawArray* loaded_scripts() const { return raw_ptr()->loaded_scripts_; }
   RawGrowableObjectArray* metadata() const { return raw_ptr()->metadata_; }
@@ -2779,6 +2779,9 @@ class Namespace : public Object {
   RawArray* show_names() const { return raw_ptr()->show_names_; }
   RawArray* hide_names() const { return raw_ptr()->hide_names_; }
 
+  void AddMetadata(intptr_t token_pos, const Class& owner_class);
+  RawObject* GetMetadata() const;
+
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(RawNamespace));
   }
@@ -2793,6 +2796,9 @@ class Namespace : public Object {
  private:
   static RawNamespace* New();
 
+  RawField* metadata_field() const { return raw_ptr()->metadata_field_; }
+  void set_metadata_field(const Field& value) const;
+
   FINAL_HEAP_OBJECT_IMPLEMENTATION(Namespace, Object);
   friend class Class;
 };