Fix gr-edit-preferences to be able to save "Indent Unit"

Change-Id: Ie3664d2d510aa572f073ccb5ad770c2b28352e57
(cherry picked from commit cd9a2a62090350f68ad4210aadda817564acaf31)
diff --git a/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences.html b/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences.html
index 782100e..b3e6990 100644
--- a/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences.html
+++ b/polygerrit-ui/app/elements/settings/gr-edit-preferences/gr-edit-preferences.html
@@ -35,6 +35,7 @@
               prevent-invalid-input
               allowed-pattern="[0-9]"
               bind-value="{{editPrefs.tab_size}}"
+              on-keypress="_handleEditPrefsChanged"
               on-change="_handleEditPrefsChanged">
         </span>
       </section>
@@ -47,6 +48,7 @@
               prevent-invalid-input
               allowed-pattern="[0-9]"
               bind-value="{{editPrefs.line_length}}"
+              on-keypress="_handleEditPrefsChanged"
               on-change="_handleEditPrefsChanged">
         </span>
       </section>
@@ -59,6 +61,7 @@
               prevent-invalid-input
               allowed-pattern="[0-9]"
               bind-value="{{editPrefs.indent_unit}}"
+              on-keypress="_handleEditPrefsChanged"
               on-change="_handleEditPrefsChanged">
         </span>
       </section>