Refactor "I scroll" web step to avoid using execute_script

The apparition driver does not support "scroll_by" without going through "execute_script", but we can better express the intention of this test and make the scrolling action a bit more general by replacing "scroll a bit" with "scroll to [some element]" — in this case, we need to scroll until the "Change" button is visible so that we can press it.

This change_settings.feature spec is the only place that used "I scroll a bit".

features/desktop/change_settings.feature

@@ -19,12 +19,12 @@ Feature: Change settings
 
   Scenario: Change my email preferences
     When I uncheck "user_email_preferences_mentioned"
-    And I scroll a bit
+    And I scroll to "change_email_preferences"
     And I press "change_email_preferences"
     Then I should see "Email notifications changed"
     And the "user_email_preferences_mentioned" checkbox should not be checked
     When I uncheck "user_email_preferences_mentioned_in_comment"
-    And I scroll a bit
+    And I scroll to "change_email_preferences"
     And I press "change_email_preferences"
     Then I should see "Email notifications changed"
     And the "user_email_preferences_mentioned_in_comment" checkbox should not be checked

features/step_definitions/custom_web_steps.rb

@@ -167,10 +167,6 @@ Then /^I should see (\d+) contacts$/ do |n_posts|
   has_css?("#people-stream .stream-element", count: n_posts.to_i).should be true
 end
 
-When /^I scroll a bit$/ do
-  page.execute_script("window.scrollBy(0,200)")
-end
-
 And /^I scroll down$/ do
   page.execute_script("window.scrollBy(0,3000000)")
 end

features/step_definitions/web_steps.rb

@@ -195,3 +195,8 @@ Then /^I wait until ajax requests finished$/ do
     loop until page.evaluate_script("jQuery.active") == 0
   end
 end
+
+When /^I scroll to "([^"]*)"$/ do |element_id|
+  element = find_by_id(element_id) # rubocop:disable Rails/DynamicFindBy
+  page.scroll_to(element, align: :bottom)
+end