[CrosDisksClient] Determine device type from DeviceMediaType property sent by cros-disks.

chrome/browser/chromeos/disks/disk_mount_manager.cc

Index: chrome/browser/chromeos/disks/disk_mount_manager.cc
diff --git a/chrome/browser/chromeos/disks/disk_mount_manager.cc b/chrome/browser/chromeos/disks/disk_mount_manager.cc
index e831ccf1a1ce2e116e1092784d5107cd031c48dd..c808d32b8133e07fa8902b9377ac0f27845bf22b 100644
--- a/chrome/browser/chromeos/disks/disk_mount_manager.cc
+++ b/chrome/browser/chromeos/disks/disk_mount_manager.cc
@@ -632,6 +632,22 @@ MountType DiskMountManager::MountTypeFromString(const std::string& type_str) {
 }
 
 // static
+std::string DiskMountManager::DeviceTypeToString(DeviceType type) {
+  switch (type) {
+    case DEVICE_TYPE_USB:
+      return "usb";
+    case DEVICE_TYPE_SD:
+      return "sd";
+    case DEVICE_TYPE_OPTICAL:
+      return "optical";
+    case DEVICE_TYPE_MOBILE:
+      return "mobile";
+    default:
+      return "unknown";
+  }
+}
+
+// static
 void DiskMountManager::Initialize() {
   if (g_disk_mount_manager) {
     LOG(WARNING) << "DiskMountManager was already initialized";