win: Add UUID::InitializeFromSystemUUID()

client/crash_report_database_win.cc

Index: client/crash_report_database_win.cc
diff --git a/client/crash_report_database_win.cc b/client/crash_report_database_win.cc
index afa39338fd71c9f81257a2df5d692a33d6dc2d57..4a32f492f36b5568d128b4c0ed754d3ff5cb2a85 100644
--- a/client/crash_report_database_win.cc
+++ b/client/crash_report_database_win.cc
@@ -584,9 +584,8 @@ OperationStatus CrashReportDatabaseWin::PrepareNewCrashReport(
   ::UUID system_uuid;
   if (UuidCreate(&system_uuid) != RPC_S_OK)
     return kFileSystemError;
-  static_assert(sizeof(system_uuid) == 16, "unexpected system uuid size");
-  static_assert(offsetof(::UUID, Data1) == 0, "unexpected uuid layout");
-  UUID uuid(reinterpret_cast<const uint8_t*>(&system_uuid.Data1));
+  UUID uuid;
+  uuid.InitializeFromSystemUUID(&system_uuid);
 
   scoped_ptr<NewReportDisk> new_report(new NewReportDisk());
   new_report->uuid = uuid;