Update clang, re-enable checker, fix issues it flags

services/files/files_test_base.h

Index: services/files/files_test_base.h
diff --git a/services/files/files_test_base.h b/services/files/files_test_base.h
index 5ca38f26c6fc22e903a5e1a8c0a9b8c25d190697..616c88130defaebe17911e488efd461c40fdd18f 100644
--- a/services/files/files_test_base.h
+++ b/services/files/files_test_base.h
@@ -84,24 +84,15 @@ Callback<void(T1, T2)> Capture(T1* t1, T2* t2) {
 
 class FilesTestBase : public test::ApplicationTestBase {
  public:
-  FilesTestBase() {}
-  ~FilesTestBase() override {}
+  FilesTestBase();
+  ~FilesTestBase() override;
 
-  void SetUp() override {
-    test::ApplicationTestBase::SetUp();
-    application_impl()->ConnectToService("mojo:files", &files_);
-  }
+  void SetUp() override;
 
  protected:
   // Note: This has an out parameter rather than returning the |DirectoryPtr|,
   // since |ASSERT_...()| doesn't work with return values.
-  void GetTemporaryRoot(DirectoryPtr* directory) {
-    Error error = ERROR_INTERNAL;
-    files()->OpenFileSystem(FILE_SYSTEM_TEMPORARY, GetProxy(directory),
-                            Capture(&error));
-    ASSERT_TRUE(files().WaitForIncomingMethodCall());
-    ASSERT_EQ(ERROR_OK, error);
-  }
+  void GetTemporaryRoot(DirectoryPtr* directory);
 
   FilesPtr& files() { return files_; }