Fix a bug that unmounting devices on the policy update can be a busy loop.

chrome/browser/chromeos/file_manager/fake_disk_mount_manager.h

Index: chrome/browser/chromeos/file_manager/fake_disk_mount_manager.h
diff --git a/chrome/browser/chromeos/file_manager/fake_disk_mount_manager.h b/chrome/browser/chromeos/file_manager/fake_disk_mount_manager.h
index 0645f6828dc872cf07f42e11fade17106e404551..ed9372ef69ebed6a1acbda5e24c3561b79e037ff 100644
--- a/chrome/browser/chromeos/file_manager/fake_disk_mount_manager.h
+++ b/chrome/browser/chromeos/file_manager/fake_disk_mount_manager.h
@@ -7,6 +7,7 @@
 
 #include <string>
 #include <vector>
+#include <queue>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
@@ -66,9 +67,16 @@ class FakeDiskMountManager : public chromeos::disks::DiskMountManager {
                  const std::string& mount_label,
                  chromeos::MountType type,
                  chromeos::MountAccessMode access_mode) override;
+  // In order to simulate asynchronous invocation of callbacks after unmount
+  // is finished, |callback| will be invoked only when
+  // |FinishAllUnmountRequest()| is called.
   void UnmountPath(const std::string& mount_path,
                    chromeos::UnmountOptions options,
                    const UnmountPathCallback& callback) override;
+  // Emulates that all mount request finished.
+  // Return true if there was one or more mount request enqueued, or false
+  // otherwise.
+  bool FinishAllUnmountPathRequests();

[fukino, 2016/09/16 07:31:34]

This is not an override of DiskMountManager.

We need to move it outside "// DiskMountManager overrides." block or remove it.

[yamaguchi, 2016/09/26 02:25:28]

Done.

   void FormatMountedDevice(const std::string& mount_path) override;
   void UnmountDeviceRecursively(
       const std::string& device_path,
@@ -80,6 +88,7 @@ class FakeDiskMountManager : public chromeos::disks::DiskMountManager {
 
  private:
   base::ObserverList<Observer> observers_;
+  std::queue<UnmountPathCallback> pending_unmount_callbacks_;
 
   DiskMap disks_;
   MountPointMap mount_points_;