Added support for cold start in image perf plugin

Summary:
This diff adds support for cold start in image perf plugin. Now developer can see which images have been requested as part of cold start.

CC: Diego Sanchez Vivian Wehner Alexander Oprisnik Gaurav Nijhara

Reviewed By: jknoxville

Differential Revision: D14227065

fbshipit-source-id: 3347b460e491b218115d8572cb8b323de909ef1b

src/plugins/fresco/ImagesSidebar.js

@@ -112,6 +112,15 @@ class EventDetails extends Component<{
             setValue={function(path: Array<string>, val: any) {}}
           />
         </p>
+        <p>
+          <DataDescriptionKey>Requested on cold start</DataDescriptionKey>
+          <span key="sep">: </span>
+          <DataDescription
+            type="number"
+            value={event.coldStart}
+            setValue={function(path: Array<string>, val: any) {}}
+          />
+        </p>
         {this.renderViewportData()}
       </EventDetails.Container>
     );

src/plugins/fresco/api.js

@@ -58,6 +58,7 @@ export type ImageEvent = {
   startTime: Timestamp,
   endTime: Timestamp,
   source: string,
+  coldStart: number,
   viewport?: ViewportData, // not set for prefetches
 };