Bug 1220196 - Explicitly set AppCompatCheckBox in xml. r=sebastian

We don't extend AppCompatActivity in GeckoApp (bug 1220309) so these
edge cases are not getting auto-inflated to their AppCompat
counterparts.

--HG--
extra : commitid : KGMyi1R3DvI
extra : rebase_source : 318ecad96502d1f5d4179b2842b874a3ffbdacb4

mobile/android/base/resources/layout/default_doorhanger.xml

@@ -22,7 +22,8 @@
               android:gravity="right"
               android:visibility="gone"/>
 
-    <CheckBox android:id="@+id/doorhanger_checkbox"
+    <android.support.v7.widget.AppCompatCheckBox
+              android:id="@+id/doorhanger_checkbox"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
               android:layout_marginTop="@dimen/doorhanger_section_padding_medium"

mobile/android/base/resources/layout/login_edit_dialog.xml

@@ -21,7 +21,8 @@
               android:inputType="textPassword"
               android:hint="@string/doorhanger_login_edit_password_hint"/>
 
-    <CheckBox android:id="@+id/checkbox_toggle_password"
+    <android.support.v7.widget.AppCompatCheckBox
+              android:id="@+id/checkbox_toggle_password"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
               android:text="@string/doorhanger_login_edit_toggle"

mobile/android/base/resources/layout/site_setting_item.xml

@@ -41,7 +41,7 @@
 
     </LinearLayout>
 
-    <CheckBox
+    <android.support.v7.widget.AppCompatCheckBox
         android:id="@+id/checkbox"
         android:layout_width="35dip"
         android:layout_height="wrap_content"