`#pragma once` for app, base, chrome, gfx, ipc, net, skia, views

BUG=50273
TEST=everything still builds, build is 10% faster on windows, same speed on mac/linux

TBR: erg

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@53716 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/base/command_line.h b/base/command_line.h
index 2c4f32d..b7f01f3 100644
--- a/base/command_line.h
+++ b/base/command_line.h
@@ -15,6 +15,7 @@
 
 #ifndef BASE_COMMAND_LINE_H_
 #define BASE_COMMAND_LINE_H_
+#pragma once
 
 #include "build/build_config.h"