base: Add ScopedJavaLocalFrame class.

base/android/scoped_java_ref.h

Index: base/android/scoped_java_ref.h
diff --git a/base/android/scoped_java_ref.h b/base/android/scoped_java_ref.h
index a5d71e2d23b9b8d7ad0447ed7c9c2b54e905c83b..7863c0bef3a21fd908e0a836f8f03240cb591660 100644
--- a/base/android/scoped_java_ref.h
+++ b/base/android/scoped_java_ref.h
@@ -14,6 +14,23 @@
 namespace base {
 namespace android {
 
+// Creates a new local reference frame, in which at least a given number of
+// local references can be created. Note that local references already created
+// in previous local frames are still valid in the current local frame.
+class BASE_EXPORT ScopedJavaLocalFrame {
+ public:
+  explicit ScopedJavaLocalFrame(JNIEnv* env);
+  ScopedJavaLocalFrame(JNIEnv* env, int capacity);
+  ~ScopedJavaLocalFrame();
+
+ private:
+  // This class is only good for use on the thread it was created on so
+  // it's safe to cache the non-threadsafe JNIEnv* inside this object.
+  JNIEnv* env_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedJavaLocalFrame);
+};
+
 // Forward declare the generic java reference template class.
 template<typename T> class JavaRef;