Fix clang syntax checking.

This fixes serveral clang syntax checking. 1) unused functions.
2) confict of struct and class. 3) unused variables.

BUG=chromium:230663
TEST=clang syntax checking passed.
     trybot daisy-release passed
Change-Id: I8dbfb7dd5f21739831843bc3e7fa8ec7864824b9
Reviewed-on: https://gerrit.chromium.org/gerrit/47997
Reviewed-by: Han Shen <shenhan@chromium.org>
Commit-Queue: Yunlian Jiang <yunlian@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
diff --git a/download_action_unittest.cc b/download_action_unittest.cc
index 81ea589..657155b 100644
--- a/download_action_unittest.cc
+++ b/download_action_unittest.cc
@@ -307,7 +307,8 @@
 };
 
 // This is a simple Action class for testing.
-struct DownloadActionTestAction : public Action<DownloadActionTestAction> {
+class DownloadActionTestAction : public Action<DownloadActionTestAction> {
+ public:
   DownloadActionTestAction() : did_run_(false) {}
   typedef InstallPlan InputObjectType;
   typedef InstallPlan OutputObjectType;