Workaround: Wrap IBusText with ibus namespace.

chromeos/dbus/ibus/ibus_text.h

Index: chromeos/dbus/ibus/ibus_text.h
diff --git a/chromeos/dbus/ibus/ibus_text.h b/chromeos/dbus/ibus/ibus_text.h
index 86ded15335e8dfdcfb3601d6be64ccf0ac7c1470..6010b129890e61dd68e406828bf4df5c14ff3380 100644
--- a/chromeos/dbus/ibus/ibus_text.h
+++ b/chromeos/dbus/ibus/ibus_text.h
@@ -16,6 +16,8 @@ class MessageReader;
 }  // dbus
 
 namespace chromeos {
+// TODO(nona): Remove ibus namespace after complete libibus removal.
+namespace ibus {
 
 // The IBusText is one of IBusObjects and it contains IBusAttrList object which
 // contains array of IBusAttribute object. The overview of each data strucutres
@@ -144,6 +146,7 @@ class CHROMEOS_EXPORT IBusText {
   DISALLOW_COPY_AND_ASSIGN(IBusText);
 };
 
+}  // namespace ibus
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_IBUS_IBUS_TEXT_H_