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

chrome/browser/chrome_browser_field_trials.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chrome_browser_field_trials.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 37 matching lines @@
 // Desktop may have to restore a lot of tabs so give it more time before doing
 // non-essential work. The spare file is still a performance boost but not as
 // significant of one so it's not required.
 constexpr bool kSpareFileRequired = false;
 constexpr int kSpareFileCreateDelaySeconds = 90;
 #endif
 
 // Check for feature enabling the use of persistent histogram storage and
 // enable the global allocator if so.
 // TODO(bcwhite): Move this and CreateInstallerFileMetricsProvider into a new
 // file and make kBrowserMetricsName local to that file.

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

Friendly ping on this! (Separate CL, but please let's get this done as otherwise
this just keeps growing and growing...)

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

Acknowledged.

 void InstantiatePersistentHistograms() {
   base::FilePath metrics_dir;
   if (!base::PathService::Get(chrome::DIR_USER_DATA, &metrics_dir))
     return;
 
-  base::FilePath metrics_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,
+      &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::ConstructFilePaths(
-      metrics_dir, ChromeMetricsServiceClient::kBrowserMetricsName,
-      &metrics_file, &active_file, &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 {
     LOCAL_MEMORY_SUCCESS,
     LOCAL_MEMORY_FAILED,
     MAPPED_FILE_SUCCESS,
     MAPPED_FILE_FAILED,
     MAPPED_FILE_EXISTS,
     NO_SPARE_FILE,
     INIT_RESULT_MAX
@@ skipping 120 matching lines @@
     bool has_seed,
     base::FeatureList* feature_list) {
   CreateFallbackSamplingTrialIfNeeded(has_seed, feature_list);
 }
 
 void ChromeBrowserFieldTrials::InstantiateDynamicTrials() {
   // Persistent histograms must be enabled as soon as possible.
   InstantiatePersistentHistograms();
   tracing::SetupBackgroundTracingFieldTrial();
 }