Modernize JS execution in PictureInPictureContentBrowserTest

Replace the semi-deprecated ExecuteScript*() functions with the modern
counterparts ExecJs(), EvalJs().

While we're here, let's make sure the test doesn't try to
requestPictureInPicture() until metadata has been loaded.

Bug: 1138168
Change-Id: Id247c2922f26e922417496f9cc406317ac061ebe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2529121
Commit-Queue: Wojciech Dzierżanowski <wdzierzanowski@opera.com>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827738}

content/test/data/media/picture_in_picture/one-video.html

@@ -16,24 +16,6 @@
       });
     }
 
-    function play() {
-      video.play()
-          .then(_ => window.domAutomationController.send(true))
-          .catch(e => window.domAutomationController.send(false));
-    }
-
-    function enterPictureInPictureAndGetResult() {
-      video.requestPictureInPicture()
-          .then(_ => window.domAutomationController.send(true))
-          .catch(e => window.domAutomationController.send(false));
-    }
-
-    function enterFullscreenAndGetResult() {
-      video.requestFullscreen()
-          .then(_ => window.domAutomationController.send(true))
-          .catch(e => window.domAutomationController.send(false));
-    }
-
     function addPlayEventListener() {
       video.addEventListener('play', () => {
         document.title = 'play';
@@ -46,6 +28,35 @@
       }, { once: true });
     }
 
+    async function play() {
+      await video.play();
+      return true;
+    }
+
+    async function enterPictureInPicture() {
+      await _waitForMetadata();
+      await video.requestPictureInPicture();
+      return true;
+    }
+
+    function _waitForMetadata() {
+      return new Promise((resolve, _) => {
+        if (video.readyState >= HTMLMediaElement.HAVE_METADATA) {
+          resolve();
+          return;
+        }
+
+        video.addEventListener('loadedmetadata', () => {
+          resolve();
+        }, { once: true });
+      });
+    }
+
+    async function enterFullscreen() {
+      await video.requestFullscreen();
+      return true;
+    }
+
     function setMediaSessionPlayActionHandler() {
       navigator.mediaSession.setActionHandler("play", _ => {
         video.play();