Makes sure that an input method doesn't reference to a destroyed object.

ui/base/ime/mock_input_method.cc

Index: ui/base/ime/mock_input_method.cc
diff --git a/ui/base/ime/mock_input_method.cc b/ui/base/ime/mock_input_method.cc
index aed83c2ba72ae349c443e91c81eaf7eb47c0d9a4..58134fa431306468c028a266ef1d37520a070c68 100644
--- a/ui/base/ime/mock_input_method.cc
+++ b/ui/base/ime/mock_input_method.cc
@@ -24,6 +24,11 @@ void MockInputMethod::SetFocusedTextInputClient(TextInputClient* client) {
     OnTextInputTypeChanged(client);
 }
 
+void MockInputMethod::DetachTextInputClient(TextInputClient* client) {
+  if (text_input_client_ == client)
+    text_input_client_ = NULL;
+}
+
 TextInputClient* MockInputMethod::GetTextInputClient() const {
   return text_input_client_;
 }