Move more utility classes from libcore to libnativehelper (part 1)

Change-Id: If51679ea9d97ed405d07fb7ccf26489f59ef208d
diff --git a/include/nativehelper/ScopedLocalFrame.h b/include/nativehelper/ScopedLocalFrame.h
new file mode 100644
index 0000000..35b6ad8
--- /dev/null
+++ b/include/nativehelper/ScopedLocalFrame.h
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef SCOPED_LOCAL_FRAME_H_included
+#define SCOPED_LOCAL_FRAME_H_included
+
+#include "JNIHelp.h"
+
+class ScopedLocalFrame {
+public:
+    ScopedLocalFrame(JNIEnv* env) : mEnv(env) {
+        mEnv->PushLocalFrame(128);
+    }
+
+    ~ScopedLocalFrame() {
+        mEnv->PopLocalFrame(NULL);
+    }
+
+private:
+    JNIEnv* mEnv;
+
+    // Disallow copy and assignment.
+    ScopedLocalFrame(const ScopedLocalFrame&);
+    void operator=(const ScopedLocalFrame&);
+};
+
+#endif  // SCOPED_LOCAL_FRAME_H_included