Put BrowserMetrics with embedded profiles into subdir for auto-upload.

chrome/browser/chrome_browser_field_trials.cc

Index: chrome/browser/chrome_browser_field_trials.cc
diff --git a/chrome/browser/chrome_browser_field_trials.cc b/chrome/browser/chrome_browser_field_trials.cc
index 3d8ea8bd6e93ed2367f84fa86d673f2aaf85a9ce..8d6b013ffd971c6a1285d49e9f5f56453bb3bb94 100644
--- a/chrome/browser/chrome_browser_field_trials.cc
+++ b/chrome/browser/chrome_browser_field_trials.cc
@@ -61,18 +61,38 @@ void InstantiatePersistentHistograms() {
   if (!base::PathService::Get(chrome::DIR_USER_DATA, &metrics_dir))
     return;
 
-  base::FilePath metrics_file;
-  base::FilePath active_file;
-  base::FilePath spare_file;
+  // Remove any existing file from its legacy location.
+  // TODO(bcwhite): Remove this block of code in M62 or later.
+  base::FilePath legacy_file;
   base::GlobalHistogramAllocator::ConstructFilePaths(
       metrics_dir, ChromeMetricsServiceClient::kBrowserMetricsName,
-      &metrics_file, &active_file, &spare_file);
+      &legacy_file, nullptr, nullptr);
+  base::PostTaskWithTraits(
+      FROM_HERE,
+      {base::MayBlock(), base::TaskPriority::BACKGROUND,
+       base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN},
+      base::BindOnce(base::IgnoreResult(&base::DeleteFile),
+                     base::Passed(&legacy_file), /*recursive=*/false));
+
+  // Create a directory for storing completed metrics files. Files in this
+  // directory must have embedded system profiles. If the directory can't be
+  // created, the file will just be deleted below.
+  base::FilePath upload_dir =
+      metrics_dir.AppendASCII(ChromeMetricsServiceClient::kBrowserMetricsName);
+  base::CreateDirectory(upload_dir);
+
+  base::FilePath upload_file;
+  base::FilePath active_file;
+  base::FilePath spare_file;
+  base::GlobalHistogramAllocator::ConstructFilePathsForUploadDir(
+      metrics_dir, upload_dir, ChromeMetricsServiceClient::kBrowserMetricsName,

[Alexei Svitkine (slow), 2017/06/28 17:30:35]

Can you add a comment about expected file locations here?

i.e. user-data-dir/BrowserMetrics/BrowserMetrics-active.pma etc.

[bcwhite, 2017/06/28 18:52:08]

Done.

+      &upload_file, &active_file, &spare_file);
 
   // Move any existing "active" file to the final name from which it will be
   // read when reporting initial stability metrics. If there is no file to
   // move, remove any old, existing file from before the previous session.
-  if (!base::ReplaceFile(active_file, metrics_file, nullptr))
-    base::DeleteFile(metrics_file, /*recursive=*/false);
+  if (!base::ReplaceFile(active_file, upload_file, nullptr))
+    base::DeleteFile(active_file, /*recursive=*/false);
 
   // This is used to report results to an UMA histogram.
   enum InitResult {