Small improvements to JNI references.

base/android/jni_weak_ref.cc

Index: base/android/jni_weak_ref.cc
diff --git a/base/android/jni_weak_ref.cc b/base/android/jni_weak_ref.cc
index 55244f2f7331c8a591f02c6051923d7ebda3b33c..53a91a8a99918f97a70fcc317e8af0a4f3dbd4f5 100644
--- a/base/android/jni_weak_ref.cc
+++ b/base/android/jni_weak_ref.cc
@@ -4,26 +4,38 @@
 
 #include "base/android/jni_weak_ref.h"
 
+#include <utility>
+
 #include "base/android/jni_android.h"
 #include "base/logging.h"
 
 using base::android::AttachCurrentThread;
 
-JavaObjectWeakGlobalRef::JavaObjectWeakGlobalRef()
-  : obj_(NULL) {
-}
+JavaObjectWeakGlobalRef::JavaObjectWeakGlobalRef() : obj_(nullptr) {}
 
 JavaObjectWeakGlobalRef::JavaObjectWeakGlobalRef(
     const JavaObjectWeakGlobalRef& orig)
-    : obj_(NULL) {
+    : obj_(nullptr) {
   Assign(orig);
 }
 
+JavaObjectWeakGlobalRef::JavaObjectWeakGlobalRef(JavaObjectWeakGlobalRef&& orig)
+    : obj_(orig.obj_) {
+  orig.obj_ = nullptr;
+}
+
 JavaObjectWeakGlobalRef::JavaObjectWeakGlobalRef(JNIEnv* env, jobject obj)
     : obj_(env->NewWeakGlobalRef(obj)) {
   DCHECK(obj_);
 }
 
+JavaObjectWeakGlobalRef::JavaObjectWeakGlobalRef(
+    JNIEnv* env,
+    const base::android::JavaRef<jobject>& obj)
+    : obj_(env->NewWeakGlobalRef(obj.obj())) {
+  DCHECK(obj_);
+}
+
 JavaObjectWeakGlobalRef::~JavaObjectWeakGlobalRef() {
   reset();
 }
@@ -32,10 +44,14 @@ void JavaObjectWeakGlobalRef::operator=(const JavaObjectWeakGlobalRef& rhs) {
   Assign(rhs);
 }
 
+void JavaObjectWeakGlobalRef::operator=(JavaObjectWeakGlobalRef&& rhs) {
+  std::swap(obj_, rhs.obj_);
+}
+
 void JavaObjectWeakGlobalRef::reset() {
   if (obj_) {
     AttachCurrentThread()->DeleteWeakGlobalRef(obj_);
-    obj_ = NULL;
+    obj_ = nullptr;
   }
 }
 
@@ -46,7 +62,7 @@ base::android::ScopedJavaLocalRef<jobject>
 
 base::android::ScopedJavaLocalRef<jobject> GetRealObject(
     JNIEnv* env, jweak obj) {
-  jobject real = NULL;
+  jobject real = nullptr;
   if (obj)
     real = env->NewLocalRef(obj);
   return base::android::ScopedJavaLocalRef<jobject>(env, real);
@@ -60,5 +76,5 @@ void JavaObjectWeakGlobalRef::Assign(const JavaObjectWeakGlobalRef& other) {
   if (obj_)
     env->DeleteWeakGlobalRef(obj_);
 
-  obj_ = other.obj_ ? env->NewWeakGlobalRef(other.obj_) : NULL;
+  obj_ = other.obj_ ? env->NewWeakGlobalRef(other.obj_) : nullptr;
 }