jni_generator: Pass object parameters as JavaParamRef.

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 37e7fd3507ca480ee29209df24d3e7e2cf2b7472..d6a81fa637f3b1214593f50d0a5d5e6989c42632 100644
--- a/base/android/scoped_java_ref.h
+++ b/base/android/scoped_java_ref.h
@@ -94,6 +94,27 @@ class JavaRef : public JavaRef<jobject> {
   DISALLOW_COPY_AND_ASSIGN(JavaRef);
 };
 
+// Holds a local reference to a JNI method parameter.
+// Method parameters should not be deleted, and so this class exists purely to
+// wrap them as a JavaRef<T> in the JNI binding generator. Do not create
+// instances manually.
+template<typename T>
+class JavaParamRef : public JavaRef<T> {
+ public:
+  // Assumes that |obj| is a parameter passed to a JNI method from Java.
+  // Does not assume ownership as parameters should not be deleted.
+  JavaParamRef(JNIEnv* env, T obj) : JavaRef<T>(env, obj) {}
+
+  ~JavaParamRef() {}
+
+  // TODO(torne): remove this cast once we're using JavaRef consistently.
+  // http://crbug.com/506850
+  operator T() const { return JavaRef<T>::obj(); }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(JavaParamRef);
+};
+
 // Holds a local reference to a Java object. The local reference is scoped
 // to the lifetime of this object.
 // Instances of this class may hold onto any JNIEnv passed into it until
@@ -208,6 +229,11 @@ class ScopedJavaGlobalRef : public JavaRef<T> {
   }
 
   template<typename U>
+  void Reset(JNIEnv* env, const JavaParamRef<U>& other) {
+    this->Reset(env, other.obj());
+  }
+
+  template<typename U>
   void Reset(JNIEnv* env, U obj) {
     implicit_cast<T>(obj);  // Ensure U is assignable to T
     this->SetNewGlobalRef(env, obj);