Bug 1567164 - Ensure StyleRuleActor.getRuleText() returns text content of minified CSS. r=gl

The patch for Bug 724505 changed the return of `prettifyCSS()` from a string to an object and the reference in the StyleRuleActor.getRuleText() was not updated. This patch fixes this and introduces a test.

Differential Revision: https://phabricator.services.mozilla.com/D38673

--HG--
extra : moz-landing-system : lando

devtools/server/actors/styles.js

@@ -1595,8 +1595,8 @@ var StyleRuleActor = protocol.ActorClassWithSpec(styleRuleSpec, {
       text = `${selectorText} {${ruleBodyText}}`;
     }
 
-    const prettyCSS = prettifyCSS(text);
-    return Promise.resolve(prettyCSS);
+    const { result } = prettifyCSS(text);
+    return Promise.resolve(result);
   },
 
   /**

devtools/server/tests/browser/browser.ini

@@ -138,6 +138,7 @@ fail-if = fission
 fail-if = fission
 [browser_storage_updates.js]
 fail-if = fission
+[browser_styles_getRuleText.js]
 [browser_stylesheets_getTextEmpty.js]
 [browser_stylesheets_nested-iframes.js]
 [browser_register_actor.js]

devtools/server/tests/browser/browser_styles_getRuleText.js

@@ -0,0 +1,35 @@
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Test that StyleRuleActor.getRuleText returns the contents of the CSS rule.
+
+const CSS_RULE = `#test {
+  background-color: #f06;
+}`;
+
+const CONTENT = `
+  <style type='text/css'>
+    ${CSS_RULE}
+  </style>
+  <div id="test"></div>
+`;
+
+const TEST_URI = `data:text/html;charset=utf-8,${encodeURIComponent(CONTENT)}`;
+
+add_task(async function() {
+  const { inspector, target, walker } = await initInspectorFront(TEST_URI);
+
+  const pageStyle = await inspector.getPageStyle();
+  const element = await walker.querySelector(walker.rootNode, "#test");
+  const entries = await pageStyle.getApplied(element, { inherited: false });
+
+  const rule = entries[1].rule;
+  const text = await rule.getRuleText();
+
+  is(text, CSS_RULE, "CSS rule text content matches");
+
+  await target.destroy();
+});