Fix page benchmark result display (#8438)

The page tested by the benchmark was changed from `notification` to
`home` in #8358, but the announce script was still expecting the
`notification` page to be in the results. It does collect results for
all pages, but the `notification` page was hard-coded to be used for
the benchmark summary.

The announce script now correctly looks for the `home` page results for
the benchmark summary. Variable names have been updated to make it more
clear what's going on here as well.

development/metamaskbot-build-announce.js

@@ -78,15 +78,17 @@ async function start () {
     }
   }
 
+  const summaryPlatform = 'chrome'
+  const summaryPage = 'home'
   let commentBody
-  if (!benchmarkResults.chrome) {
-    console.log(`No results for Chrome found; skipping benchmark`)
+  if (!benchmarkResults[summaryPlatform]) {
+    console.log(`No results for ${summaryPlatform} found; skipping benchmark`)
     commentBody = artifactsBody
   } else {
     try {
-      const chromePageLoad = Math.round(parseFloat(benchmarkResults.chrome.notification.average.load))
-      const chromePageLoadMarginOfError = Math.round(parseFloat(benchmarkResults.chrome.notification.marginOfError.load))
-      const benchmarkSummary = `Page Load Metrics (${chromePageLoad} ± ${chromePageLoadMarginOfError} ms)`
+      const summaryPageLoad = Math.round(parseFloat(benchmarkResults[summaryPlatform][summaryPage].average.load))
+      const summaryPageLoadMarginOfError = Math.round(parseFloat(benchmarkResults[summaryPlatform][summaryPage].marginOfError.load))
+      const benchmarkSummary = `Page Load Metrics (${summaryPageLoad} ± ${summaryPageLoadMarginOfError} ms)`
 
       const allPlatforms = new Set()
       const allPages = new Set()