Add a method to remount all removable devices in DiskMountManager.

chromeos/disks/disk_mount_manager.h

Index: chromeos/disks/disk_mount_manager.h
diff --git a/chromeos/disks/disk_mount_manager.h b/chromeos/disks/disk_mount_manager.h
index 39d114dba4b3c59a495af4b7a082cd8ea95d01b3..cceebc0983d9c7db7c6a9113c6765720a6ce89b1 100644
--- a/chromeos/disks/disk_mount_manager.h
+++ b/chromeos/disks/disk_mount_manager.h
@@ -165,6 +165,8 @@ class CHROMEOS_EXPORT DiskMountManager {
 
     void clear_mount_path() { mount_path_.clear(); }
 
+    bool is_mounted() const { return !mount_path_.empty(); }
+
    private:
     std::string device_path_;
     std::string mount_path_;
@@ -294,6 +296,10 @@ class CHROMEOS_EXPORT DiskMountManager {
                            UnmountOptions options,
                            const UnmountPathCallback& callback) = 0;
 
+  // Remounts mounted removable devices to change the read-only mount option.
+  // Devices that can be mounted only in its read-only mode will be ignored.
+  virtual void RemountAllRemovableDrives(chromeos::MountAccessMode mode) = 0;
+
   // Formats Device given its mount path. Unmounts the device.
   // Example: mount_path: /media/VOLUME_LABEL
   virtual void FormatMountedDevice(const std::string& mount_path) = 0;