Lower the priority of environment and process data collection.

chrome/browser/safe_browsing/incident_reporting/environment_data_collection.cc

Index: chrome/browser/safe_browsing/incident_reporting/environment_data_collection.cc
diff --git a/chrome/browser/safe_browsing/incident_reporting/environment_data_collection.cc b/chrome/browser/safe_browsing/incident_reporting/environment_data_collection.cc
index f207502a3ac742370b8253646d1c654def211c02..10c3b6c1f254c1564ba026c466ad86587f6e9603 100644
--- a/chrome/browser/safe_browsing/incident_reporting/environment_data_collection.cc
+++ b/chrome/browser/safe_browsing/incident_reporting/environment_data_collection.cc
@@ -8,6 +8,7 @@
 
 #include "base/cpu.h"
 #include "base/sys_info.h"
+#include "base/threading/platform_thread.h"
 #include "chrome/common/channel_info.h"
 #include "chrome/common/safe_browsing/csd.pb.h"
 #include "components/version_info/version_info.h"
@@ -62,6 +63,11 @@ void CollectProcessData(ClientIncidentReport_EnvironmentData_Process* process) {
 }  // namespace
 
 void CollectEnvironmentData(ClientIncidentReport_EnvironmentData* data) {
+  // Lower priority for this task.

[gab, 2015/12/08 16:21:33]

If we're going to do this I think we should add:

// Toggling priority only makes sense in a thread pool.
DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());

here as IMO it only makes sense to do this in a pool (on a message loop this
would preempt other tasks -- arguably it could also in a thread pool if this
becomes the norm but it isn't just yet and the new task_scheduler API should
provide a sane way to do this before we get there).

[proberge, 2015/12/08 16:39:03]

Done.

+  auto previous_priority = base::PlatformThread::GetCurrentThreadPriority();
+  base::PlatformThread::SetCurrentThreadPriority(
+      base::ThreadPriority::BACKGROUND);
+
   // OS
   {
     ClientIncidentReport_EnvironmentData_OS* os = data->mutable_os();
@@ -82,6 +88,9 @@ void CollectEnvironmentData(ClientIncidentReport_EnvironmentData* data) {
 
   // Process
   CollectProcessData(data->mutable_process());
+
+  // Reset the thread priority.
+  base::PlatformThread::SetCurrentThreadPriority(previous_priority);
 }
 
 #if !defined(OS_WIN)