Adjust theming acceptance tests to new header colour transition

Before, the acceptance tests checked the header colour just once, as the
header colour was immediately changed once the new theming colour was
saved. This is no longer the case, as currently a transition is used to
change between the original colour and the new one, so now the
acceptance tests check repeteadly for the expected header colour until
it matches or the timeout expires.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

tests/acceptance/features/app-theming.feature

@@ -5,10 +5,13 @@ Feature: app-theming
     And I visit the settings page
     And I open the "Theming" section
     And I see that the color selector in the Theming app has loaded
-    And I see that the header color is "#0082C9"
+    # The "eventually" part is not really needed here, as the colour is not
+    # being animated at this point, but there is no need to create a specific
+    # step just for this.
+    And I see that the header color is eventually "#0082C9"
     When I set the "Color" parameter in the Theming app to "#C9C9C9"
     Then I see that the parameters in the Theming app are eventually saved
-    And I see that the header color is "#C9C9C9"
+    And I see that the header color is eventually "#C9C9C9"
 
   Scenario: resetting the color updates the header color
     Given I am logged in as the admin
@@ -17,7 +20,7 @@ Feature: app-theming
     And I see that the color selector in the Theming app has loaded
     And I set the "Color" parameter in the Theming app to "#C9C9C9"
     And I see that the parameters in the Theming app are eventually saved
-    And I see that the header color is "#C9C9C9"
+    And I see that the header color is eventually "#C9C9C9"
     When I reset the "Color" parameter in the Theming app to its default value
     Then I see that the parameters in the Theming app are eventually saved
-    And I see that the header color is "#0082C9"
+    And I see that the header color is eventually "#0082C9"

tests/acceptance/features/bootstrap/ThemingAppContext.php

@@ -125,13 +125,20 @@ class ThemingAppContext implements Context, ActorAwareInterface {
 	}
 
 	/**
-	 * @Then I see that the header color is :color
+	 * @Then I see that the header color is eventually :color
 	 */
-	public function iSeeThatTheHeaderColorIs($color) {
-		$headerColor = $this->actor->getSession()->evaluateScript("return $('#header').css('background-color');");
-		$headerColor = $this->getRGBArray($headerColor);
-		$color = $this->getRGBArray($color);
-		PHPUnit_Framework_Assert::assertEquals($color, $headerColor);
+	public function iSeeThatTheHeaderColorIsEventually($color) {
+		$headerColorMatchesCallback = function() use($color) {
+			$headerColor = $this->actor->getSession()->evaluateScript("return $('#header').css('background-color');");
+			$headerColor = $this->getRGBArray($headerColor);
+			$color = $this->getRGBArray($color);
+
+			return $headerColor == $color;
+		};
+
+		if (!Utils::waitFor($headerColorMatchesCallback, $timeout = 10 * $this->actor->getFindTimeoutMultiplier(), $timeoutStep = 1)) {
+			PHPUnit_Framework_Assert::fail("The header color is not $color yet after $timeout seconds");
+		}
 	}
 
 	/**