Clarify UI strings are button labels

lighthouse-core/report/html/renderer/code-snippet-renderer.js

@@ -43,9 +43,9 @@ class CodeSnippetRenderer {
     const header = dom.cloneTemplate('#tmpl-lh-code-snippet__header', tmpl);
     dom.find('.lh-code-snippet__title', header).textContent = title;
 
-    const {codeSnippetCollapse, codeSnippetExpand} = Util.UIStrings;
-    dom.find('.' + SHOW_IF_EXPANDED_CLASS, header).textContent = codeSnippetCollapse;
-    dom.find('.' + SHOW_IF_COLLAPSED_CLASS, header).textContent = codeSnippetExpand;
+    const {codeSnippetCollapseBtnLabel, codeSnippetExpandBtnLabel} = Util.UIStrings;
+    dom.find('.' + SHOW_IF_EXPANDED_CLASS, header).textContent = codeSnippetCollapseBtnLabel;
+    dom.find('.' + SHOW_IF_COLLAPSED_CLASS, header).textContent = codeSnippetExpandBtnLabel;
 
     const toggleExpandButton = dom.find('.lh-code-snippet__toggle-expand', header);
     // If we're already showing all the lines of the snippet, we don't need an expand/collapse

lighthouse-core/report/html/renderer/util.js

@@ -536,9 +536,9 @@ Util.UIStrings = {
   crcLongestDurationLabel: 'Maximum critical path latency:',
 
   /** Label for button that shows all lines of the code snippet when clicked */
-  codeSnippetExpand: 'Expand snippet',
+  codeSnippetExpandBtnLabel: 'Expand snippet',
   /** Label for button that only shows a few lines of the code snippet when clicked */
-  codeSnippetCollapse: 'Collapse snippet',
+  codeSnippetCollapseBtnLabel: 'Collapse snippet',
 
   /** Explanation shown to users below performance results to inform them that the test was done with a 4G network connection and to warn them that the numbers they see will likely change slightly the next time they run Lighthouse. 'Lighthouse' becomes link text to additional documentation. */
   lsPerformanceCategoryDescription: '[Lighthouse](https://developers.google.com/web/tools/lighthouse/) analysis of the current page on an emulated mobile network. Values are estimated and may vary.',