Implement ftl::TaskRunner::PostTaskForTime function. (#3165)

DEPS

@@ -54,7 +54,7 @@ deps = {
    # and not have to specific specific hashes.
 
   'src/lib/ftl':
-   Var('fuchsia_git') + '/ftl' + '@' + '5e9935c7205c119ce05098dc1d9c8eaac0595ba4',
+   Var('fuchsia_git') + '/ftl' + '@' + 'e8d8bf108418d5de96971ecd04b7cc0a58d8a568',
 
   'src/lib/tonic':
    Var('fuchsia_git') + '/tonic' + '@' + 'e1d221b924cb2a604363a8a9dd393d319becc0e8',

glue/task_runner_adaptor.cc

@@ -30,6 +30,16 @@ void TaskRunnerAdaptor::PostTask(ftl::Closure task) {
   runner_->PostTask(FROM_HERE, base::Bind(RunClosure, task));
 }
 
+void TaskRunnerAdaptor::PostTaskForTime(ftl::Closure task,
+                                        ftl::TimePoint target_time) {
+  ftl::TimePoint now = ftl::TimePoint::Now();
+  runner_->PostDelayedTask(FROM_HERE, base::Bind(RunClosure, task),
+                           target_time <= now
+                               ? base::TimeDelta()
+                               : base::TimeDelta::FromMicroseconds(
+                                     (target_time - now).ToMicroseconds()));
+}
+
 void TaskRunnerAdaptor::PostDelayedTask(ftl::Closure task,
                                         ftl::TimeDelta delay) {
   runner_->PostDelayedTask(

glue/task_runner_adaptor.h

@@ -19,6 +19,7 @@ class TaskRunnerAdaptor : public ftl::TaskRunner {
   explicit TaskRunnerAdaptor(scoped_refptr<base::TaskRunner> runner);
 
   void PostTask(ftl::Closure task) override;
+  void PostTaskForTime(ftl::Closure task, ftl::TimePoint target_time) override;
   void PostDelayedTask(ftl::Closure task, ftl::TimeDelta delay) override;
   bool RunsTasksOnCurrentThread() override;