Diagnostics: Temporary styles for cpu chart

https://screenshot.googleplex.com/AYbxBNBccTZfMbZ

Bug: 1125150
Change-Id: I123b7f0c29dc3c6004e0e7a299c5102b20a9b0fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2450895Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Commit-Queue: Joon Ahn <joonbug@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814284}

chromeos/components/diagnostics_ui/resources/realtime_cpu_chart.html

 <style include="diagnostics-shared diagnostics-fonts">
+  #chart-wrapper {
+    width: 300px;
+    border: #000 1px dotted;
+  }
+
+  #chart-wrapper > div {
+    font-size: 24px;
+  }
 </style>
 
 <div id="chart-wrapper">