Remove use of capturePixelsAsyncThen() which will be removed.

This switches to using updateAllLifecyclePhasesAndComposite() instead,
which doesn't pretend to return pixels.

R=yangguo@chromium.org

Bug: 866140, 1069111, 952399
Change-Id: If4ea6117cf176e3649ee4394ae913a404f1652c1
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2208540
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>

front_end/performance_test_runner/TimelineTestRunner.js

@@ -436,7 +436,7 @@ TestRunner.deprecatedInitAsync(`
     let promise = new Promise(fulfill => callback = fulfill);
 
     if (window.testRunner)
-      testRunner.capturePixelsAsyncThen(callback);
+      testRunner.updateAllLifecyclePhasesAndCompositeThen(callback);
     else
       window.requestAnimationFrame(callback);