Don't cut off precision of performance.now on Worker RAF

Before, performance.now used to be unsafe to expose to users.
Now performance.now() is safe to be exposed to users (and it is on the IDL),
so RAF doesn't need to do its own cut.

Bug: 995235
Change-Id: Ib547abcd0d05cc81d3d461420725c74cffcc826c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1801224
Commit-Queue: Fernando Serboncini <fserb@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Auto-Submit: Fernando Serboncini <fserb@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#696042}

third_party/blink/renderer/core/workers/worker_animation_frame_provider.cc

@@ -47,8 +47,6 @@ void WorkerAnimationFrameProvider::BeginFrame() {
                     WorkerGlobalScopePerformance::performance(
                         *To<WorkerGlobalScope>(context));
                 double time = performance->now();
-                // We don't want to expose microseconds residues to users.
-                time = round(time * 60) / 60;
 
                 provider->callback_collection_.ExecuteFrameCallbacks(time,
                                                                      time);