base: Add ScopedJavaLocalFrame class.

base/android/scoped_java_ref.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_ANDROID_SCOPED_JAVA_REF_H_
 #define BASE_ANDROID_SCOPED_JAVA_REF_H_
 
 #include <jni.h>
 #include <stddef.h>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 
 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;
 
 // Template specialization of JavaRef, which acts as the base class for all
 // other JavaRef<> template types. This allows you to e.g. pass
 // ScopedJavaLocalRef<jstring> into a function taking const JavaRef<jobject>&
 template<>
 class BASE_EXPORT JavaRef<jobject> {
  public:
   jobject obj() const { return obj_; }
@@ skipping 162 matching lines @@
   // global reference when it is done with it.
   T Release() {
     return static_cast<T>(this->ReleaseInternal());
   }
 };
 
 }  // namespace android
 }  // namespace base
 
 #endif  // BASE_ANDROID_SCOPED_JAVA_REF_H_