`#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/version.h b/base/version.h
index 776ebe6..99e6650 100644
--- a/base/version.h
+++ b/base/version.h
@@ -4,6 +4,7 @@
 
 #ifndef BASE_VERSION_H_
 #define BASE_VERSION_H_
+#pragma once
 
 #include <string>
 #include <vector>