Use static_cast instead of reinterpret_cast for downcasting

static_cast is better suited for downcasting since it can check that the
types are related.

/chrome/browser/chromeos/policy
This CL was uploaded by git cl split.

R=rsorokin@chromium.org

Change-Id: I5c0f9ac978d5e6c7ed3b71690ea29a734e7e1fc7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2435819
Auto-Submit: Kevin McNee <mcnee@chromium.org>
Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811763}

chrome/browser/chromeos/policy/device_local_account_browsertest.cc

@@ -1352,8 +1352,9 @@ IN_PROC_BROWSER_TEST_F(DeviceLocalAccountTest, ExternalData) {
   // verify that the underlying policy subsystem will start a fetch
   // without this request as well, the user_manager::UserManager must be
   // prevented from seeing the policy change.
-  reinterpret_cast<chromeos::ChromeUserManagerImpl*>(
-      user_manager::UserManager::Get())->StopPolicyObserverForTesting();
+  static_cast<chromeos::ChromeUserManagerImpl*>(
+      user_manager::UserManager::Get())
+      ->StopPolicyObserverForTesting();
 
   UploadDeviceLocalAccountPolicy();
   AddPublicSessionToDevicePolicy(kAccountId1);