Store resolved library prefix in unresolved class object in order not to repeat

runtime/vm/class_finalizer.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/class_finalizer.h"
 
 #include "vm/flags.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
 #include "vm/longjump.h"
@@ skipping 243 matching lines @@
     OS::Print("VerifyBootstrapClasses END.\n");
   }
   Isolate::Current()->heap()->Verify();
 }
 
 
 // Resolve unresolved_class in the library of cls.
 RawClass* ClassFinalizer::ResolveClass(
     const Class& cls, const UnresolvedClass& unresolved_class) {
   Library& lib = Library::Handle();
-  if (unresolved_class.qualifier() == String::null()) {
+  if (unresolved_class.library_prefix() == LibraryPrefix::null()) {
     lib = cls.library();
   } else {
-    const String& qualifier = String::Handle(unresolved_class.qualifier());
     LibraryPrefix& lib_prefix = LibraryPrefix::Handle();
-    lib_prefix = cls.LookupLibraryPrefix(qualifier);
-    if (lib_prefix.IsNull()) {
-      const Script& script = Script::Handle(cls.script());
-      ReportError(script, unresolved_class.token_index(),
-                  "cannot resolve library prefix '%s' from '%s'.\n",
-                  qualifier.ToCString(),
-                  String::Handle(cls.Name()).ToCString());
-    }
+    lib_prefix = unresolved_class.library_prefix();
+    ASSERT(!lib_prefix.IsNull());
     lib = lib_prefix.library();
   }
   ASSERT(!lib.IsNull());
   const String& class_name = String::Handle(unresolved_class.ident());
   const Class& resolved_class = Class::Handle(lib.LookupClass(class_name));
   if (resolved_class.IsNull()) {
     const Script& script = Script::Handle(cls.script());
     ReportError(script, unresolved_class.token_index(),
                 "cannot resolve class name '%s' from '%s'.\n",
                 String::Handle(unresolved_class.Name()).ToCString(),
@@ skipping 992 matching lines @@
   va_end(args);
   if (FLAG_warning_as_error) {
     Isolate::Current()->long_jump_base()->Jump(1, error);
     UNREACHABLE();
   } else {
     OS::Print("%s", error.ToErrorCString());
   }
 }
 
 }  // namespace dart