Revert "Enable Persistent Histograms on iOS"

This reverts commit d9fd02e.

CleanupBrowserMetricsDataFiles() is added to remove all accumulated
BrowserMetrics/ files.

(cherry picked from commit e9bd0a2)

Bug: 992946
Change-Id: I29c96bf49101c1954185208ca80b6e432e91e8c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1755004
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Peter Lee <pkl@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#687104}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1755192
Reviewed-by: Kariah Davis <kariahda@chromium.org>
Cr-Commit-Position: refs/branch-heads/3882@{#4}
Cr-Branched-From: 382570a-refs/heads/master@{#686622}

ios/chrome/browser/ios_chrome_field_trials.cc

@@ -4,18 +4,6 @@
 
 #include "ios/chrome/browser/ios_chrome_field_trials.h"
 
-#include "base/path_service.h"
-#include "components/metrics/persistent_histograms.h"
-#include "ios/chrome/browser/chrome_paths.h"
-
-void IOSChromeFieldTrials::SetupFieldTrials() {
-  // Persistent histograms must be enabled as soon as possible.
-  base::FilePath user_data_dir;
-  if (base::PathService::Get(ios::DIR_USER_DATA, &user_data_dir)) {
-    InstantiatePersistentHistograms(user_data_dir);
-  }
-}
-
 void IOSChromeFieldTrials::SetupFeatureControllingFieldTrials(
     bool has_seed,
     base::FeatureList* feature_list) {

ios/chrome/browser/ios_chrome_field_trials.h

@@ -16,7 +16,7 @@ class IOSChromeFieldTrials : public variations::PlatformFieldTrials {
   ~IOSChromeFieldTrials() override {}
 
   // variations::PlatformFieldTrials:
-  void SetupFieldTrials() override;
+  void SetupFieldTrials() override {}
   void SetupFeatureControllingFieldTrials(
       bool has_seed,
       base::FeatureList* feature_list) override;

ios/chrome/browser/metrics/ios_chrome_metrics_service_client.mm

@@ -14,11 +14,14 @@
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
+#include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/path_service.h"
 #include "base/process/process_metrics.h"
 #include "base/rand_util.h"
 #include "base/strings/string16.h"
+#include "base/task/post_task.h"
 #include "base/threading/platform_thread.h"
 #include "components/crash/core/common/crash_keys.h"
 #include "components/history/core/browser/history_service.h"
@@ -33,6 +36,7 @@
 #include "components/metrics/net/cellular_logic_helper.h"
 #include "components/metrics/net/net_metrics_log_uploader.h"
 #include "components/metrics/net/network_metrics_provider.h"
+#include "components/metrics/persistent_histograms.h"
 #include "components/metrics/stability_metrics_helper.h"
 #include "components/metrics/ui/screen_info_metrics_provider.h"
 #include "components/metrics/url_constants.h"
@@ -77,6 +81,24 @@ void GetNetworkConnectionTrackerAsync(
       GetApplicationContext()->GetNetworkConnectionTracker());
 }
 
+void CleanupBrowserMetricsDataFiles() {
+  base::FilePath user_data_dir;
+  if (!base::PathService::Get(ios::DIR_USER_DATA, &user_data_dir))
+    return;
+  base::FilePath browser_metrics_upload_dir =
+      user_data_dir.AppendASCII(kBrowserMetricsName);
+  if (base::IsDirectoryEmpty(browser_metrics_upload_dir))
+    return;
+  // Delete accumulated metrics files due to http://crbug/992946
+  base::PostTask(
+      FROM_HERE,
+      {base::ThreadPool(), base::MayBlock(), base::TaskPriority::BEST_EFFORT,
+       base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN},
+      base::BindOnce(base::IgnoreResult(&base::DeleteFile),
+                     std::move(browser_metrics_upload_dir),
+                     /*recursive=*/true));
+}
+
 }  // namespace
 
 IOSChromeMetricsServiceClient::IOSChromeMetricsServiceClient(
@@ -244,6 +266,10 @@ void GetNetworkConnectionTrackerAsync(
   metrics_service_->RegisterMetricsProvider(
       std::make_unique<metrics::DemographicMetricsProvider>(
           std::make_unique<metrics::ChromeBrowserStateClient>()));
+
+  // TODO(crbug.com/992946): This is an interim fix to stop logging of
+  // persistent histograms and delete any accumulated metrics files.
+  CleanupBrowserMetricsDataFiles();
 }
 
 void IOSChromeMetricsServiceClient::CollectFinalHistograms() {