Implemented a "Last Updated" field for the about page of Chrome OS.

base/sys_info.h

Index: base/sys_info.h
diff --git a/base/sys_info.h b/base/sys_info.h
index f3677d6009f0e67147642c54a470fb3c97a3bde2..5230aef1147ce5a4f439c3545d8ff2df3cb788f8 100644
--- a/base/sys_info.h
+++ b/base/sys_info.h
@@ -8,6 +8,7 @@
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/time.h"
 
 #include <string>
 
@@ -61,7 +62,7 @@ class BASE_EXPORT SysInfo {
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
   // Returns the maximum SysV shared memory segment size.
   static size_t MaxSharedMemorySize();
-#endif
+#endif // defined(OS_POSIX) && !defined(OS_MACOSX)
 
 #if defined(OS_CHROMEOS)
   // Returns the name of the version entry we wish to look up in the
@@ -74,7 +75,16 @@ class BASE_EXPORT SysInfo {
                               int32* major_version,
                               int32* minor_version,
                               int32* bugfix_version);
-#endif
+
+  // Retrieves the approximate time at which Chrome OS was last updated. Each
+  // time a new build is created, /etc/lsb-release is modified with the new
+  // version numbers of the release. This function reads that file's metadata
+  // and sets |time| equal to the time at which it was last modified, a close
+  // approximation to the time the last Chrome OS update occurred. On success,
+  // this function returns |true|, and if a problem is encountered, it returns
+  // |false|.
+  static bool GetTimeLastUpdated(base::Time* time);
+#endif // defined(OS_CHROMEOS)
 };
 
 }  // namespace base