Defer Posting StoreMetricsClientInfo During PreCreateThreads

chrome/browser/metrics/chrome_metrics_services_manager_client.cc

Index: chrome/browser/metrics/chrome_metrics_services_manager_client.cc
diff --git a/chrome/browser/metrics/chrome_metrics_services_manager_client.cc b/chrome/browser/metrics/chrome_metrics_services_manager_client.cc
index 82a5a10ac877320c1b619cf3acae581465813315..628d8ce881270f4263a65781184b0dd60d171275 100644
--- a/chrome/browser/metrics/chrome_metrics_services_manager_client.cc
+++ b/chrome/browser/metrics/chrome_metrics_services_manager_client.cc
@@ -59,9 +59,18 @@ const base::Feature kMetricsReportingFeature{"MetricsReporting",
 // Posts |GoogleUpdateSettings::StoreMetricsClientInfo| on blocking pool thread
 // because it needs access to IO and cannot work from UI thread.
 void PostStoreMetricsClientInfo(const metrics::ClientInfo& client_info) {
-  content::BrowserThread::GetBlockingPool()->PostTask(
-      FROM_HERE,
-      base::Bind(&GoogleUpdateSettings::StoreMetricsClientInfo, client_info));
+  // The delayed post task allows this function to get called before the
+  // blocking pool is ready to go.

[gab, 2016/12/13 15:58:39]

(this sentence is backwards?)

// Posting the task from the main message loop ensures the blocking pool is
initialized (which it isn't always at this point).

[robliao, 2016/12/13 18:19:38]

Clarified to
// The message loop processes messages after the blocking pool is initialized.
// Posting a task to the message loop to post a task to the blocking pool
// ensures that the blocking pool is ready to accept tasks at that time.

+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI, FROM_HERE,
+      base::Bind(
+          [](const metrics::ClientInfo& client_info) {
+            content::BrowserThread::PostBlockingPoolTask(
+                FROM_HERE,
+                base::Bind(&GoogleUpdateSettings::StoreMetricsClientInfo,
+                           client_info));
+          },
+          client_info));
 }
 
 // Appends a group to the sampling controlling |trial|. The group will be