Eliminate all but one top-level class per library.

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 9b335ebfff5af92f56739ad2af6b7c12c67a3e9d..8d73f0c58f1bff609222f0c464d040d2ae700738 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -741,8 +741,9 @@ class RawPatchClass : public RawObject {
   }
   RawClass* patched_class_;
   RawClass* source_class_;
+  RawScript* script_;
   RawObject** to() {
-    return reinterpret_cast<RawObject**>(&ptr()->source_class_);
+    return reinterpret_cast<RawObject**>(&ptr()->script_);
   }
 
   friend class Function;
@@ -977,7 +978,7 @@ class RawLibrary : public RawObject {
   RawString* private_key_;
   RawArray* dictionary_;         // Top-level names in this library.
   RawGrowableObjectArray* metadata_;  // Metadata on classes, methods etc.
-  RawArray* anonymous_classes_;  // Classes containing top-level elements.
+  RawClass* toplevel_class_;  // Class containing top-level elements.
   RawGrowableObjectArray* patch_classes_;
   RawArray* imports_;            // List of Namespaces imported without prefix.
   RawArray* exports_;            // List of re-exported Namespaces.
@@ -994,7 +995,6 @@ class RawLibrary : public RawObject {
   Dart_NativeEntryResolver native_entry_resolver_;  // Resolves natives.
   Dart_NativeEntrySymbol native_entry_symbol_resolver_;
   classid_t index_;             // Library id number.
-  classid_t num_anonymous_;     // Number of entries in anonymous_classes_.
   uint16_t num_imports_;        // Number of entries in imports_.
   int8_t load_state_;           // Of type LibraryState.
   bool corelib_imported_;