jni: Pass method parameters as JavaParamRef in printing.

Pass all object parameters to JNI methods in JavaParamRef<> wrappers.
This matches previous changes made to do this for JNI non-method
functions.

BUG=519562
R=avayvod@chromium.org

Review URL: https://codereview.chromium.org/1477783002

Cr-Commit-Position: refs/heads/master@{#361696}

printing/printing_context_android.cc

@@ -103,9 +103,10 @@ void PrintingContextAndroid::AskUserForSettings(
   }
 }
 
-void PrintingContextAndroid::AskUserForSettingsReply(JNIEnv* env,
-                                                     jobject obj,
-                                                     jboolean success) {
+void PrintingContextAndroid::AskUserForSettingsReply(
+    JNIEnv* env,
+    const JavaParamRef<jobject>& obj,
+    jboolean success) {
   if (!success) {
     // TODO(cimamoglu): Differentiate between FAILED And CANCEL.
     callback_.Run(FAILED);
@@ -137,8 +138,9 @@ void PrintingContextAndroid::AskUserForSettingsReply(JNIEnv* env,
   callback_.Run(OK);
 }
 
-void PrintingContextAndroid::ShowSystemDialogDone(JNIEnv* env,
-                                                  jobject obj) {
+void PrintingContextAndroid::ShowSystemDialogDone(
+    JNIEnv* env,
+    const JavaParamRef<jobject>& obj) {
   // Settings are not updated, callback is called only to unblock javascript.
   callback_.Run(CANCEL);
 }

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,