diff --git a/runtime/bin/gen_snapshot.cc b/runtime/bin/gen_snapshot.cc
index af9741e..c1f304b 100644
--- a/runtime/bin/gen_snapshot.cc
+++ b/runtime/bin/gen_snapshot.cc
@@ -420,10 +420,18 @@
 
   if ((load_compilation_trace_filename != NULL) &&
       ((snapshot_kind == kCoreJIT) || (snapshot_kind == kAppJIT))) {
+    // Finalize all classes. This ensures that there are no non-finalized
+    // classes in the gaps between cid ranges. Such classes prevent merging of
+    // cid ranges.
+    Dart_Handle result = Dart_FinalizeAllClasses();
+    CHECK_RESULT(result);
+    // Sort classes to have better cid ranges.
+    result = Dart_SortClasses();
+    CHECK_RESULT(result);
     uint8_t* buffer = NULL;
     intptr_t size = 0;
     ReadFile(load_compilation_trace_filename, &buffer, &size);
-    Dart_Handle result = Dart_LoadCompilationTrace(buffer, size);
+    result = Dart_LoadCompilationTrace(buffer, size);
     free(buffer);
     CHECK_RESULT(result);
   }
diff --git a/runtime/include/dart_native_api.h b/runtime/include/dart_native_api.h
index 39b29ff..3b8f4d2 100644
--- a/runtime/include/dart_native_api.h
+++ b/runtime/include/dart_native_api.h
@@ -170,4 +170,9 @@
 
 DART_EXPORT DART_WARN_UNUSED_RESULT Dart_Handle Dart_ReadAllBytecode();
 
+/**
+ * Finalizes all classes.
+ */
+DART_EXPORT DART_WARN_UNUSED_RESULT Dart_Handle Dart_FinalizeAllClasses();
+
 #endif /* INCLUDE_DART_NATIVE_API_H_ */ /* NOLINT */
diff --git a/runtime/vm/compiler/aot/precompiler.cc b/runtime/vm/compiler/aot/precompiler.cc
index 29b1fad..9fa7585 100644
--- a/runtime/vm/compiler/aot/precompiler.cc
+++ b/runtime/vm/compiler/aot/precompiler.cc
@@ -2172,32 +2172,9 @@
 }
 
 void Precompiler::FinalizeAllClasses() {
-  Library& lib = Library::Handle(Z);
-  Class& cls = Class::Handle(Z);
-
-  for (intptr_t i = 0; i < libraries_.Length(); i++) {
-    lib ^= libraries_.At(i);
-    if (!lib.Loaded()) {
-      String& uri = String::Handle(Z, lib.url());
-      String& msg = String::Handle(
-          Z,
-          String::NewFormatted("Library '%s' is not loaded. "
-                               "Did you forget to call Dart_FinalizeLoading?",
-                               uri.ToCString()));
-      Jump(Error::Handle(Z, ApiError::New(msg)));
-    }
-
-    ClassDictionaryIterator it(lib, ClassDictionaryIterator::kIteratePrivate);
-    while (it.HasNext()) {
-      cls = it.GetNextClass();
-      if (cls.IsDynamicClass()) {
-        continue;  // class 'dynamic' is in the read-only VM isolate.
-      }
-      error_ = cls.EnsureIsFinalized(T);
-      if (!error_.IsNull()) {
-        Jump(error_);
-      }
-    }
+  error_ = Library::FinalizeAllClasses();
+  if (!error_.IsNull()) {
+    Jump(error_);
   }
   I->set_all_classes_finalized(true);
 }
diff --git a/runtime/vm/native_api_impl.cc b/runtime/vm/native_api_impl.cc
index 9bf957d..df1859d 100644
--- a/runtime/vm/native_api_impl.cc
+++ b/runtime/vm/native_api_impl.cc
@@ -217,4 +217,24 @@
 #endif  // defined(DART_PRECOMPILED_RUNTIME)
 }
 
+DART_EXPORT Dart_Handle Dart_FinalizeAllClasses() {
+#if defined(DART_PRECOMPILED_RUNTIME)
+  return Api::NewError("%s: All classes are already finalized in AOT runtime.",
+                       CURRENT_FUNC);
+#else
+  DARTSCOPE(Thread::Current());
+  API_TIMELINE_DURATION(T);
+  Dart_Handle result = Api::CheckAndFinalizePendingClasses(T);
+  if (Api::IsError(result)) {
+    return result;
+  }
+  CHECK_CALLBACK_STATE(T);
+  const Error& error = Error::Handle(T->zone(), Library::FinalizeAllClasses());
+  if (!error.IsNull()) {
+    return Api::NewHandle(T, error.raw());
+  }
+  return Api::Success();
+#endif  // defined(DART_PRECOMPILED_RUNTIME)
+}
+
 }  // namespace dart
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 84843f7c..8045887 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -12228,6 +12228,39 @@
 }
 
 #if !defined(DART_PRECOMPILED_RUNTIME)
+
+RawError* Library::FinalizeAllClasses() {
+  Thread* thread = Thread::Current();
+  ASSERT(thread->IsMutatorThread());
+  Zone* zone = thread->zone();
+  Error& error = Error::Handle(zone);
+  const GrowableObjectArray& libs = GrowableObjectArray::Handle(
+      Isolate::Current()->object_store()->libraries());
+  Library& lib = Library::Handle(zone);
+  Class& cls = Class::Handle(zone);
+  for (int i = 0; i < libs.Length(); i++) {
+    lib ^= libs.At(i);
+    if (!lib.Loaded()) {
+      String& uri = String::Handle(zone, lib.url());
+      String& msg = String::Handle(
+          zone,
+          String::NewFormatted("Library '%s' is not loaded. "
+                               "Did you forget to call Dart_FinalizeLoading?",
+                               uri.ToCString()));
+      return ApiError::New(msg);
+    }
+    ClassDictionaryIterator it(lib, ClassDictionaryIterator::kIteratePrivate);
+    while (it.HasNext()) {
+      cls = it.GetNextClass();
+      error = cls.EnsureIsFinalized(thread);
+      if (!error.IsNull()) {
+        return error.raw();
+      }
+    }
+  }
+  return Error::null();
+}
+
 RawError* Library::ReadAllBytecode() {
   Thread* thread = Thread::Current();
   ASSERT(thread->IsMutatorThread());
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index bb7200a..08216a2 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -4024,6 +4024,8 @@
   // Eagerly compile all classes and functions in the library.
   static RawError* CompileAll(bool ignore_error = false);
 #if !defined(DART_PRECOMPILED_RUNTIME)
+  // Finalize all classes in all libraries.
+  static RawError* FinalizeAllClasses();
   // Eagerly read all bytecode.
   static RawError* ReadAllBytecode();
 #endif