Wait to fetch image data a few times in Watchdog.

server/src/watchdog.js

@@ -107,14 +107,47 @@ exports.submit = function(shot) {
   const imageId = imageUrl.split("/").pop();
   const form = new FormData();
 
-  Shot.getRawBytesForClip(
-    imageId
-  ).then((obj) => {
-    if (obj === null) {
-      const err = new Error("Unable to fetch image for Watchdog submission.");
-      err.imageId = String(imageId);
-      throw err;
-    }
+  // When this is called the shot has been successfully saved to the database,
+  // but the image data is not necessarily on S3 as the save to S3 is not
+  // awaited. Awaiting the S3 upload will affect the responsiveness of saving a
+  // shot with the addon.
+  //
+  // We'll give the S3 upload a head start and try a few times to fetch the
+  // image data. This is called for every shot saved, so let's keep it simple
+  // and minimal.
+
+  const delay = function(waitInMs) {
+    return new Promise((resolve) => {
+      setTimeout(() => resolve(), waitInMs);
+    });
+  };
+
+  const getRawBytesPromise = function(timeToWait, retry) {
+    return new Promise((resolve, reject) => {
+      delay(timeToWait)
+      .then(() => Shot.getRawBytesForClip(imageId))
+      .then(obj => {
+        if (obj === null) {
+          const err = new Error("Shot image expired, blocked, or not found.");
+          err.imageId = String(imageId);
+          reject(err);
+        } else {
+          resolve(obj);
+        }
+      })
+      .catch(e => {
+        if (!retry) {
+          reject(e);
+        }
+        resolve(null);
+      });
+    });
+  };
+
+  getRawBytesPromise(1000, true)
+  .then(bytes => bytes || getRawBytesPromise(1000, true))
+  .then(bytes => bytes || getRawBytesPromise(1000))
+  .then((obj) => {
     form.append("image", obj.data, {
       filename: imageId,
       contentType: obj.contentType