mediaview: Implement ArcDocumentsProviderBackendDelegate.

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util.h

 // Copyright 2016 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.
 //
 // Utilities for ARC documents provider file system.
 
 #ifndef CHROME_BROWSER_CHROMEOS_ARC_FILEAPI_ARC_DOCUMENTS_PROVIDER_UTIL_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_FILEAPI_ARC_DOCUMENTS_PROVIDER_UTIL_H_
 
 #include <string>
 
 #include "base/files/file_path.h"
 
+class GURL;
+
 namespace storage {
 class FileSystemURL;
 }  // namespace storage
 
 namespace arc {
 
 // The name of ARC documents provider file system mount point.
 extern const char kDocumentsProviderMountPointName[];
 
 // The path of ARC documents provider file system mount point.
 extern const base::FilePath::CharType kDocumentsProviderMountPointPath[];
 
 // MIME type for directories in Android.
 // Defined as DocumentsContract.Document.MIME_TYPE_DIR in Android.
 extern const char kAndroidDirectoryMimeType[];
 
 // Parses a FileSystemURL pointing to ARC documents provider file system.
 // On success, true is returned. All arguments must not be nullptr.
 bool ParseDocumentsProviderUrl(const storage::FileSystemURL& url,
                                std::string* authority,
                                std::string* root_document_id,
                                base::FilePath* path);
 
+// C++ implementation of DocumentsContract.buildDocumentUri() in Android.
+GURL BuildDocumentUrl(const std::string& authority,
+                      const std::string& document_id);
+
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_FILEAPI_ARC_DOCUMENTS_PROVIDER_UTIL_H_