jni: Pass method parameters as JavaParamRef in content.

content/browser/android/web_contents_observer_proxy.cc

Index: content/browser/android/web_contents_observer_proxy.cc
diff --git a/content/browser/android/web_contents_observer_proxy.cc b/content/browser/android/web_contents_observer_proxy.cc
index 923f5a6bdd3c27d05f1ec57bed63c755a4a6a1fd..22ab07c2ed66946ab0e12e4f4a8bbfdffe2a4dbb 100644
--- a/content/browser/android/web_contents_observer_proxy.cc
+++ b/content/browser/android/web_contents_observer_proxy.cc
@@ -48,7 +48,8 @@ jlong Init(JNIEnv* env,
   return reinterpret_cast<intptr_t>(native_observer);
 }
 
-void WebContentsObserverProxy::Destroy(JNIEnv* env, jobject obj) {
+void WebContentsObserverProxy::Destroy(JNIEnv* env,
+                                       const JavaParamRef<jobject>& obj) {
   delete this;
 }