add pause button for resumable in-progress downloads.

chrome/browser/android/download/download_manager_service.h

 // 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.
 
 #ifndef CHROME_BROWSER_ANDROID_DOWNLOAD_DOWNLOAD_MANAGER_SERVICE_H_
 #define CHROME_BROWSER_ANDROID_DOWNLOAD_DOWNLOAD_MANAGER_SERVICE_H_
 
 #include <jni.h>
 #include <string>
 
@@ skipping 22 matching lines @@
   // If the DownloadItem is not yet created, retry after a while.
   void ResumeDownload(JNIEnv* env,
                       jobject obj,
                       uint32_t download_id,
                       jstring fileName);
 
   // Called to cancel a download item that has ID equal to |download_id|.
   // If the DownloadItem is not yet created, retry after a while.
   void CancelDownload(JNIEnv* env, jobject obj, uint32_t download_id);
 
+  // Called to pause a download item that has ID equal to |download_id|.
+  // If the DownloadItem is not yet created, do nothing as it is already paused.
+  void PauseDownload(JNIEnv* env, jobject obj, uint32_t download_id);
+
   // content::DownloadManager::Observer methods.
   void ManagerGoingDown(content::DownloadManager* manager) override;
 
  private:
   // For testing.
   friend class DownloadManagerServiceTest;
 
   // Resume downloading the given DownloadItem.
   void ResumeDownloadItem(content::DownloadItem* item,
                           const std::string& fileName);
@@ skipping 21 matching lines @@
 
   // Download manager this class observes
   content::DownloadManager* manager_;
 
   ResumeCallback resume_callback_for_testing_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadManagerService);
 };
 
 #endif  // CHROME_BROWSER_ANDROID_DOWNLOAD_DOWNLOAD_MANAGER_SERVICE_H_