update engine: clang formatting

Fix clang formatting issues for all .cc, .h, and .proto files
in update engine.

~/trunk/src/chromium/src/buildtools/linux64/clang-format -i \
-style=file $(find update_engine -name '*.h' -o -name '*.cc' \
-o -name '*.cpp' -o -name '*.c')

BUG=b:169679497
TEST=CQ pass

Change-Id: I4fde01d3e734dbffaa2c7e7b667503d310abccae
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2462840
Reviewed-by: Amin Hassani <[email protected]>
Reviewed-by: Jae Hoon Kim <[email protected]>
Tested-by: Vyshu Khota <[email protected]>
Commit-Queue: Vyshu Khota <[email protected]>
diff --git a/common/subprocess.h b/common/subprocess.h
index 179a5c5..2ed8b81 100644
--- a/common/subprocess.h
+++ b/common/subprocess.h
@@ -37,7 +37,7 @@
 #include <brillo/process.h>
 #include <brillo/process_reaper.h>
 #endif  // __CHROMEOS__
-#include <gtest/gtest_prod.h>  // for FRIEND_TEST
+#include <gtest/gtest_prod.h>
 
 // The Subprocess class is a singleton. It's used to spawn off a subprocess
 // and get notified when the subprocess exits. The result of Exec() can