add pause button for resumable in-progress downloads.

chrome/browser/android/download/download_manager_service.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/android/download/download_manager_service.h"
 
 #include "base/android/jni_string.h"
 #include "base/message_loop/message_loop.h"
 #include "base/time/time.h"
 #include "chrome/browser/profiles/profile_manager.h"
@@ skipping 49 matching lines @@
   ResumeDownloadInternal(download_id, ConvertJavaStringToUTF8(env, fileName),
                          true);
 }
 
 void DownloadManagerService::CancelDownload(JNIEnv* env,
                                             jobject obj,
                                             uint32_t download_id) {
   CancelDownloadInternal(download_id, true);
 }
 
+void DownloadManagerService::PauseDownload(JNIEnv* env,
+                                            jobject obj,
+                                            uint32_t download_id) {
+  content::DownloadItem* item = manager_->GetDownload(download_id);
+  if (item)
+    item->Pause();
+}
+
 void DownloadManagerService::ManagerGoingDown(
     content::DownloadManager* manager) {
   manager_ = nullptr;
 }
 
 void DownloadManagerService::ResumeDownloadItem(content::DownloadItem* item,
                                                 const std::string& fileName) {
   if (!item->CanResume()) {
     OnResumptionFailed(item->GetId(), fileName);
     return;
@@ skipping 55 matching lines @@
                                                 const std::string& fileName) {
   if (!java_ref_.is_null()) {
     JNIEnv* env = base::android::AttachCurrentThread();
     Java_DownloadManagerService_onResumptionFailed(
         env, java_ref_.obj(), download_id,
         ConvertUTF8ToJavaString(env, fileName).obj());
   }
   if (!resume_callback_for_testing_.is_null())
     resume_callback_for_testing_.Run(false);
 }