Adding readme, privacy section, reducing resolution of analytics data.

src/components/intro/index.tsx

@@ -129,6 +129,11 @@ export default class Intro extends Component<Props, State> {
         <ul class={style.relatedLinks}>
           <li><a href="https://github.com/GoogleChromeLabs/squoosh/">View the code</a></li>
           <li><a href="https://github.com/GoogleChromeLabs/squoosh/issues">Report a bug</a></li>
+          <li>
+            <a href="https://github.com/GoogleChromeLabs/squoosh/blob/master/README.md#privacy">
+              Privacy
+            </a>
+          </li>
         </ul>
       </div>
     );

src/components/results/index.tsx

@@ -60,11 +60,16 @@ export default class Results extends Component<Props, State> {
 
   @bind
   onDownload() {
+    // GA can’t do floats. So we round to ints. We're deliberately rounding to nearest kilobyte to
+    // avoid cases where exact image sizes leak something interesting about the user.
+    const before = Math.round(this.props.source!.file.size / 1024);
+    const after = Math.round(this.props.imageFile!.size / 1024);
+    const change = Math.round(after / before * 1000);
+
     ga('send', 'event', 'compression', 'download', {
-      // GA can’t do floats. So we round to ints.
-      metric1: Math.floor(this.props.source!.file.size),
-      metric2: Math.floor(this.props.imageFile!.size),
-      metric3: Math.floor(this.props.imageFile!.size / this.props.source!.file.size * 1000),
+      metric1: before,
+      metric2: after,
+      metric3: change,
     });
   }