jni: Pass method parameters as JavaParamRef in printing.

printing/printing_context_android.h

Index: printing/printing_context_android.h
diff --git a/printing/printing_context_android.h b/printing/printing_context_android.h
index c0d84be0e1c07610e04b44e8ca1b8bf00f1a9370..26ebea640c479f16e4fb316e659f574b01deafe2 100644
--- a/printing/printing_context_android.h
+++ b/printing/printing_context_android.h
@@ -27,10 +27,13 @@ class PRINTING_EXPORT PrintingContextAndroid : public PrintingContext {
 
   // Called from Java, when printing settings from the user are ready or the
   // printing operation is canceled.
-  void AskUserForSettingsReply(JNIEnv* env, jobject obj, jboolean success);
+  void AskUserForSettingsReply(JNIEnv* env,
+                               const base::android::JavaParamRef<jobject>& obj,
+                               jboolean success);
 
   // Called from Java, when a printing process initiated by a script finishes.
-  void ShowSystemDialogDone(JNIEnv* env, jobject obj);
+  void ShowSystemDialogDone(JNIEnv* env,
+                            const base::android::JavaParamRef<jobject>& obj);
 
   // PrintingContext implementation.
   void AskUserForSettings(int max_pages,