Cleanup: Fix some misc issues in Linux media galleries MTP code.

chrome/browser/media_galleries/linux/mtp_device_delegate_impl_linux.cc

 // Copyright (c) 2012 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/media_galleries/linux/mtp_device_delegate_impl_linux.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/strings/string_util.h"
 #include "chrome/browser/media_galleries/linux/mtp_device_task_helper.h"
 #include "chrome/browser/media_galleries/linux/mtp_device_task_helper_map_service.h"
 #include "chrome/browser/media_galleries/linux/snapshot_file_details.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/base/io_buffer.h"
 
 namespace {
 
 // File path separator constant.
 const char kRootPath[] = "/";
 
 // Returns the device relative file path given |file_path|.
 // E.g.: If the |file_path| is "/usb:2,2:12345/DCIM" and |registered_dev_path|
 // is "/usb:2,2:12345", this function returns the device relative path which is
-// "/DCIM".
+// "DCIM".
+// In the special case when |registered_dev_path| and |file_path| are the same,
+// return |kRootPath|.
 std::string GetDeviceRelativePath(const base::FilePath& registered_dev_path,
                                   const base::FilePath& file_path) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
   DCHECK(!registered_dev_path.empty());
   DCHECK(!file_path.empty());
-  if (registered_dev_path == file_path)
-    return kRootPath;
-
-  base::FilePath relative_path;
-  if (!registered_dev_path.AppendRelativePath(file_path, &relative_path))
-    return std::string();
-  DCHECK(!relative_path.empty());
-  return relative_path.value();
+  std::string result;
+  if (registered_dev_path == file_path) {
+    result = kRootPath;
+  } else {
+    base::FilePath relative_path;
+    if (registered_dev_path.AppendRelativePath(file_path, &relative_path)) {
+      DCHECK(!relative_path.empty());
+      result = relative_path.value();
+    }
+  }
+  return result;
 }
 
 // Returns the MTPDeviceTaskHelper object associated with the MTP device
 // storage.
 //
 // |storage_name| specifies the name of the storage device.
 // Returns NULL if the |storage_name| is no longer valid (e.g. because the
 // corresponding storage device is detached, etc).
 MTPDeviceTaskHelper* GetDeviceTaskHelperForStorage(
     const std::string& storage_name) {
@@ skipping 456 matching lines @@
   task_in_progress_ = false;
   ProcessNextPendingRequest();
 }
 
 void CreateMTPDeviceAsyncDelegate(
     const std::string& device_location,
     const CreateMTPDeviceAsyncDelegateCallback& callback) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
   callback.Run(new MTPDeviceDelegateImplLinux(device_location));
 }