Enable MetricKit

After discussion with chrome-privacy, this can be enabled for
users who have opted-in UMA.

Bug: 1017434
Change-Id: I140dac0327206846127be4befa3e6c9fca8780fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2292510
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791894}

ios/chrome/app/application_delegate/BUILD.gn

@@ -5,11 +5,6 @@
 import("//build/buildflag_header.gni")
 import("//ios/chrome/features.gni")
 
-buildflag_header("ios_enable_metrickit_buildflags") {
-  header = "ios_enable_metrickit_buildflags.h"
-  flags = [ "IOS_ENABLE_METRICKIT=$ios_enable_metrickit" ]
-}
-
 source_set("application_delegate") {
   sources = [
     "memory_warning_helper.h",
@@ -131,12 +126,9 @@ source_set("metric_kit_subscriber") {
   sources = [
     "metric_kit_subscriber.h",
     "metric_kit_subscriber.mm",
-    "metric_kit_subscribing_util.h",
-    "metric_kit_subscribing_util.mm",
   ]
   frameworks = [ "MetricKit.framework" ]
   deps = [
-    ":ios_enable_metrickit_buildflags",
     "//base",
     "//components/version_info",
   ]
@@ -159,7 +151,7 @@ source_set("application_delegate_internal") {
   ]
   deps = [
     ":application_delegate",
-    ":ios_enable_metrickit_buildflags",
+    ":metric_kit_subscriber",
     ":tab_opening",
     ":url_opener_params",
     "//base",
@@ -214,9 +206,6 @@ source_set("application_delegate_internal") {
   ]
   public_deps = [ "//ios/chrome/browser/ui/scoped_ui_blocker" ]
 
-  if (ios_enable_metrickit) {
-    deps += [ ":metric_kit_subscriber" ]
-  }
   frameworks = [
     "CoreSpotlight.framework",
     "UIKit.framework",

ios/chrome/app/application_delegate/metric_kit_subscriber.h

@@ -12,8 +12,12 @@ extern NSString* const kChromeMetricKitPayloadsDirectory;
 
 // A subscriber that save MetricKit reports to the application document
 // directory.
+API_AVAILABLE(ios(13.0))
 @interface MetricKitSubscriber : NSObject <MXMetricManagerSubscriber>
 + (instancetype)sharedInstance;
+
+// Whether the MetricKit collection is enabled.
+@property(nonatomic, assign, getter=isEnabled) BOOL enabled;
 @end
 
 #endif  // IOS_CHROME_APP_APPLICATION_DELEGATE_METRIC_KIT_SUBSCRIBER_H_

ios/chrome/app/application_delegate/metric_kit_subscriber.mm

@@ -44,6 +44,8 @@ enum MetricKitExitReason {
 
 namespace {
 
+NSString* const kEnableMetricKit = @"EnableMetricKit";
+
 #if defined(__IPHONE_14_0) && __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_14_0
 void ReportExitReason(base::HistogramBase* histogram,
                       MetricKitExitReason bucket,
@@ -147,14 +149,29 @@ void WriteDiagnosticPayloads(NSArray<MXDiagnosticPayload*>* payloads)
   return instance;
 }
 
+- (void)setEnabled:(BOOL)enable {
+  if (enable == _enabled) {
+    return;
+  }
+  _enabled = enable;
+  if (enable) {
+    [[MXMetricManager sharedManager] addSubscriber:self];
+  } else {
+    [[MXMetricManager sharedManager] removeSubscriber:self];
+  }
+}
+
 - (void)didReceiveMetricPayloads:(NSArray<MXMetricPayload*>*)payloads
     API_AVAILABLE(ios(13.0)) {
-  base::ThreadPool::PostTask(
-      FROM_HERE,
-      {base::TaskPriority::BEST_EFFORT,
-       base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN,
-       base::ThreadPolicy::PREFER_BACKGROUND, base::MayBlock()},
-      base::BindOnce(WriteMetricPayloads, payloads));
+  NSUserDefaults* standard_defaults = [NSUserDefaults standardUserDefaults];
+  if ([standard_defaults boolForKey:kEnableMetricKit]) {
+    base::ThreadPool::PostTask(
+        FROM_HERE,
+        {base::TaskPriority::BEST_EFFORT,
+         base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN,
+         base::ThreadPolicy::PREFER_BACKGROUND, base::MayBlock()},
+        base::BindOnce(WriteMetricPayloads, payloads));
+  }
   for (MXMetricPayload* payload : payloads) {
     [self processPayload:payload];
   }
@@ -295,12 +312,15 @@ void WriteDiagnosticPayloads(NSArray<MXDiagnosticPayload*>* payloads)
 #if defined(__IPHONE_14_0) && __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_14_0
 - (void)didReceiveDiagnosticPayloads:(NSArray<MXDiagnosticPayload*>*)payloads
     API_AVAILABLE(ios(14.0)) {
-  base::ThreadPool::PostTask(
-      FROM_HERE,
-      {base::TaskPriority::BEST_EFFORT,
-       base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN,
-       base::ThreadPolicy::PREFER_BACKGROUND, base::MayBlock()},
-      base::BindOnce(WriteDiagnosticPayloads, payloads));
+  NSUserDefaults* standard_defaults = [NSUserDefaults standardUserDefaults];
+  if ([standard_defaults boolForKey:kEnableMetricKit]) {
+    base::ThreadPool::PostTask(
+        FROM_HERE,
+        {base::TaskPriority::BEST_EFFORT,
+         base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN,
+         base::ThreadPolicy::PREFER_BACKGROUND, base::MayBlock()},
+        base::BindOnce(WriteDiagnosticPayloads, payloads));
+  }
 }
 #endif
 

ios/chrome/app/application_delegate/metric_kit_subscriber_unittest.mm

@@ -34,16 +34,22 @@ base::FilePath MetricKitReportDirectory() {
 
   return base::FilePath(base::SysNSStringToUTF8(metric_kit_report_directory));
 }
+
+NSString* const kEnableMetricKit = @"EnableMetricKit";
 }
 
 class MetricKitSubscriberTest : public PlatformTest {
  public:
   MetricKitSubscriberTest() {
     base::DeletePathRecursively(MetricKitReportDirectory());
+    NSUserDefaults* standard_defaults = [NSUserDefaults standardUserDefaults];
+    [standard_defaults setBool:YES forKey:kEnableMetricKit];
   }
 
   ~MetricKitSubscriberTest() override {
     base::DeletePathRecursively(MetricKitReportDirectory());
+    NSUserDefaults* standard_defaults = [NSUserDefaults standardUserDefaults];
+    [standard_defaults removeObjectForKey:kEnableMetricKit];
   }
 
  private:

ios/chrome/app/application_delegate/metric_kit_subscribing_util.h

-// Copyright 2020 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.
-
-#ifndef IOS_CHROME_APP_APPLICATION_DELEGATE_METRIC_KIT_SUBSCRIBING_UTIL_H_
-#define IOS_CHROME_APP_APPLICATION_DELEGATE_METRIC_KIT_SUBSCRIBING_UTIL_H_
-
-// Enables MetricKit payloads collection and saving.
-// Payloads will be saved in JSON files in application Documents directory.
-//
-// Checks if the collection is enabled in experimental settings.
-// Changing the value of the setting will require restarting Chrome.
-void EnableMetricKitReportCollection();
-
-#endif  // IOS_CHROME_APP_APPLICATION_DELEGATE_METRIC_KIT_SUBSCRIBING_UTIL_H_

ios/chrome/app/application_delegate/metric_kit_subscribing_util.mm

-// Copyright 2020 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.
-
-#import "ios/chrome/app/application_delegate/metric_kit_subscribing_util.h"
-
-#import <Foundation/Foundation.h>
-#import <MetricKit/MetricKit.h>
-
-#import "ios/chrome/app/application_delegate/metric_kit_subscriber.h"
-
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
-namespace {
-
-// The Experimental setting that enables the collection of MetricKit reports.
-NSString* const kEnableMetricKit = @"EnableMetricKit";
-
-}  // namespace
-
-void EnableMetricKitReportCollection() {
-  static dispatch_once_t once_token;
-  dispatch_once(&once_token, ^{
-    if (@available(iOS 13, *)) {
-      NSUserDefaults* standard_defaults = [NSUserDefaults standardUserDefaults];
-      if ([standard_defaults boolForKey:kEnableMetricKit]) {
-        [[MXMetricManager sharedManager]
-            addSubscriber:[MetricKitSubscriber sharedInstance]];
-      }
-    }
-  });
-}

ios/chrome/app/application_delegate/metrics_mediator.mm

@@ -18,7 +18,7 @@
 #include "components/metrics/metrics_service.h"
 #include "components/prefs/pref_service.h"
 #include "components/ukm/ios/features.h"
-#import "ios/chrome/app/application_delegate/ios_enable_metrickit_buildflags.h"
+#import "ios/chrome/app/application_delegate/metric_kit_subscriber.h"
 #import "ios/chrome/app/application_delegate/startup_information.h"
 #include "ios/chrome/browser/application_context.h"
 #include "ios/chrome/browser/chrome_url_constants.h"
@@ -41,10 +41,6 @@
 #import "ios/web/public/web_state.h"
 #include "url/gurl.h"
 
-#if BUILDFLAG(IOS_ENABLE_METRICKIT)
-#import "ios/chrome/app/application_delegate/metric_kit_subscribing_util.h"  // nogncheck
-#endif  // BUILDFLAG(IOS_ENABLE_METRICKIT)
-
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
@@ -229,9 +225,9 @@ using metrics_mediator::kAppEnteredBackgroundDateKey;
   [self setBreakpadEnabled:optIn withUploading:allowUploading];
   [self setWatchWWANEnabled:optIn];
   [self setAppGroupMetricsEnabled:optIn];
-#if BUILDFLAG(IOS_ENABLE_METRICKIT)
-  EnableMetricKitReportCollection();
-#endif
+  if (@available(iOS 13, *)) {
+    [[MetricKitSubscriber sharedInstance] setEnabled:optIn];
+  }
 }
 
 - (BOOL)areMetricsEnabled {