Created a helper function "FindDiskBySourcePath" in DiskMountManager.

chrome/browser/chromeos/extensions/file_browser_private_apitest.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 <stdio.h>
 
 #include "base/stl_util.h"
 #include "chrome/browser/chromeos/disks/mock_disk_mount_manager.h"
 #include "chrome/browser/extensions/extension_apitest.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "content/public/browser/browser_thread.h"
 #include "webkit/fileapi/file_system_context.h"
 #include "webkit/fileapi/file_system_mount_point_provider.h"
 
 using ::testing::_;
+using ::testing::AnyNumber;
 using ::testing::ReturnRef;
 using ::testing::StrEq;
 using content::BrowserContext;
 
 using chromeos::disks::DiskMountManager;
 
 namespace {
 
 struct TestDiskInfo {
   const char* system_path;
@@ skipping 117 matching lines @@
   }
 
   // ExtensionApiTest override
   virtual void SetUpInProcessBrowserTestFixture() OVERRIDE {
     ExtensionApiTest::SetUpInProcessBrowserTestFixture();
 
     disk_mount_manager_mock_ = new chromeos::disks::MockDiskMountManager;
     chromeos::disks::DiskMountManager::InitializeForTesting(
         disk_mount_manager_mock_);
     disk_mount_manager_mock_->SetupDefaultReplies();
+
+    // OVERRIDE FindDiskBySourcePath mock function.
+    ON_CALL(*disk_mount_manager_mock_, FindDiskBySourcePath(_)).
+        WillByDefault(Invoke(
+            this, &ExtensionFileBrowserPrivateApiTest::FindVolumeBySourcePath));
   }
 
   // ExtensionApiTest override
   virtual void TearDownInProcessBrowserTestFixture() OVERRIDE {
     chromeos::disks::DiskMountManager::Shutdown();
     disk_mount_manager_mock_ = NULL;
 
     ExtensionApiTest::TearDownInProcessBrowserTestFixture();
   }
 
@@ skipping 38 matching lines @@
                 kTestDisks[disk_info_index].has_media,
                 kTestDisks[disk_info_index].on_boot_device,
                 kTestDisks[disk_info_index].is_hidden
             )
         ));
 
       }
     }
   }
 
+  const DiskMountManager::Disk* FindVolumeBySourcePath(
+      const std::string& source_path) {
+    DiskMountManager::DiskMap::const_iterator volume_it =
+        volumes_.find(source_path);
+    return (volume_it == volumes_.end()) ? NULL : volume_it->second;
+  }
+
  protected:
   chromeos::disks::MockDiskMountManager* disk_mount_manager_mock_;
   DiskMountManager::DiskMap volumes_;
   DiskMountManager::MountPointMap mount_points_;
 
  private:
   FilePath test_mount_point_;
 };
 
 IN_PROC_BROWSER_TEST_F(ExtensionFileBrowserPrivateApiTest, FileBrowserMount) {
   // We will call fileBrowserPrivate.unmountVolume once. To test that method, we
   // check that UnmountPath is really called with the same value.
   AddTmpMountPoint();
   EXPECT_CALL(*disk_mount_manager_mock_, UnmountPath(_))
       .Times(0);
   EXPECT_CALL(*disk_mount_manager_mock_,
               UnmountPath(StrEq("/media/archive/archive_mount_path"))).Times(1);
 
   EXPECT_CALL(*disk_mount_manager_mock_, disks())
       .WillRepeatedly(ReturnRef(volumes_));
 
   EXPECT_CALL(*disk_mount_manager_mock_, mount_points())
       .WillRepeatedly(ReturnRef(mount_points_));
 
   ASSERT_TRUE(RunComponentExtensionTest("filebrowser_mount"))  << message_;
 }