Add task scheduler and cpu_sampler information to slow-reports.

This CL is turning on the CPU sampler category.
  see: https://chromium-review.googlesource.com/c/chromium/src/+/1191745/

It's also turning on the task scheduler info. Which is adding the
task_priority to the trace and will ease finding priority inversion.

  Title          TaskTracker::RunTask
  Category       task_scheduler
  Args
    task_info    {execution_mode: "parallel", task_priority: "USER_BLOCKING"}


R=etiennep@chromium.org, oysteine@chromium.org

Bug: 867931
Change-Id: I8f6e4772816cc446a25c04ce0cda4b9d45c44232
Reviewed-on: https://chromium-review.googlesource.com/1199567
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588179}

chrome/common/trace_event_args_whitelist.cc

@@ -30,9 +30,10 @@ const WhitelistEntry kEventArgsWhitelist[] = {
     {"__metadata", "typeNames", nullptr},
     {"ipc", "GpuChannelHost::Send", nullptr},
     {"ipc", "SyncChannel::Send", nullptr},
-    {"toplevel", "*", nullptr},
     {"latencyInfo", "*", kInputLatencyAllowedArgs},
-    {"omnibox", "HistoryQuickProvider::Start", nullptr},
+    {"task_scheduler", "*", nullptr},
+    {"toplevel", "*", nullptr},
+    {TRACE_DISABLED_BY_DEFAULT("cpu_profiler"), "StackCpuSampling", nullptr},
     // Redefined the string since MemoryDumpManager::kTraceCategory causes
     // static initialization of this struct.
     {TRACE_DISABLED_BY_DEFAULT("memory-infra"), "*", kMemoryDumpAllowedArgs},

content/browser/tracing/background_tracing_manager_impl.cc

@@ -669,7 +669,8 @@ TraceConfig BackgroundTracingManagerImpl::GetConfigForCategoryPreset(
     case BackgroundTracingConfigImpl::CategoryPreset::BENCHMARK_NAVIGATION: {
       auto config = TraceConfig(
           "benchmark,toplevel,ipc,base,browser,navigation,omnibox,"
-          "safe_browsing,disabled-by-default-system_stats",
+          "safe_browsing,task_scheduler,task_scheduler_diagnostics"
+          "disabled-by-default-system_stats,disabled-by-default-cpu_profiler",
           record_mode);
       // Filter only browser process events.
       base::trace_event::TraceConfig::ProcessFilterConfig process_config(