Fix cpplint errors.

The only non-obvious change here is the switch from dynamic_cast to
static_cast in three cases of down-casting in UpdateAttempter.
dynamic_cast is banned by style, nor does it add any safety in this
particular case (subsequent code dereferences the result right away
without checking whether it's null).

BUG=None
TEST=None

Change-Id: I9d49b46362feaf9c6fa13b2715ebe9fe50308a9a
Reviewed-on: https://chromium-review.googlesource.com/207470
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
diff --git a/http_common.h b/http_common.h
index 51e9e7a..a4f7bdc 100644
--- a/http_common.h
+++ b/http_common.h
@@ -5,8 +5,8 @@
 // This file contains general definitions used in implementing, testing and
 // emulating communication over HTTP.
 
-#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_COMMON_H_
-#define CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_COMMON_H_
+#ifndef UPDATE_ENGINE_HTTP_COMMON_H_
+#define UPDATE_ENGINE_HTTP_COMMON_H_
 
 #include <cstdlib>
 
@@ -59,4 +59,4 @@
 
 }  // namespace chromeos_update_engine
 
-#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_HTTP_COMMON_H_
+#endif  // UPDATE_ENGINE_HTTP_COMMON_H_