Add metrics event reporting for Chrome OS

This adds a mechanism to report statistically-interesting
events to Chrome OS listeners.  A Chrome OS daemon (such
as the memory daemon "memd") can register as a client
of the Metrics Event Service, and receive signals on the
occurrence of related events (for instance, a tab discard).

This CL adds the supporting machinery and its first use,
signaling of a tab discard.

CQ-DEPEND=CL:1199965
BUG=chromium:729335
TEST=ran on DUT, verified that D-Bus signal is sent as expected

Change-Id: I6eddf4b0d18aa4c8a3fd4aab7f0770d87ddc7aeb
Reviewed-on: https://chromium-review.googlesource.com/1062078
Commit-Queue: Luigi Semenzato <semenzato@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589639}

DEPS

@@ -599,7 +599,7 @@ deps = {
 
   # For Linux and Chromium OS.
   'src/third_party/cros_system_api': {
-      'url': Var('chromium_git') + '/chromiumos/platform/system_api.git' + '@' + 'f64e5e47cf0b18553c5dee4626356c53751e90ec',
+      'url': Var('chromium_git') + '/chromiumos/platform/system_api.git' + '@' + '41fa3011067832b0b4341de834cd7cd341099738',
       'condition': 'checkout_linux',
   },
 

chrome/browser/chromeos/BUILD.gn

@@ -82,6 +82,7 @@ source_set("chromeos") {
     "//chromeos:cryptohome_proto",
     "//chromeos:cryptohome_signkey_proto",
     "//chromeos:login_manager_proto",
+    "//chromeos:metrics_event_proto",
     "//chromeos/assistant:buildflags",
     "//chromeos/components/drivefs",
     "//chromeos/components/drivefs/mojom",
@@ -610,6 +611,8 @@ source_set("chromeos") {
     "dbus/drive_file_stream_service_provider.h",
     "dbus/kiosk_info_service_provider.cc",
     "dbus/kiosk_info_service_provider.h",
+    "dbus/metrics_event_service_provider.cc",
+    "dbus/metrics_event_service_provider.h",
     "dbus/proxy_resolution_service_provider.cc",
     "dbus/proxy_resolution_service_provider.h",
     "dbus/screen_lock_service_provider.cc",
@@ -1911,6 +1914,7 @@ copy("dbus_service_files") {
     "dbus/org.chromium.ComponentUpdaterService.conf",
     "dbus/org.chromium.DriveFileStreamService.conf",
     "dbus/org.chromium.KioskAppService.conf",
+    "dbus/org.chromium.MetricsEventService.conf",
     "dbus/org.chromium.NetworkProxyService.conf",
     "dbus/org.chromium.ScreenLockService.conf",
     "dbus/org.chromium.VirtualFileRequestService.conf",

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

@@ -49,6 +49,7 @@
 #include "chrome/browser/chromeos/dbus/component_updater_service_provider.h"
 #include "chrome/browser/chromeos/dbus/drive_file_stream_service_provider.h"
 #include "chrome/browser/chromeos/dbus/kiosk_info_service_provider.h"
+#include "chrome/browser/chromeos/dbus/metrics_event_service_provider.h"
 #include "chrome/browser/chromeos/dbus/proxy_resolution_service_provider.h"
 #include "chrome/browser/chromeos/dbus/screen_lock_service_provider.h"
 #include "chrome/browser/chromeos/dbus/virtual_file_request_service_provider.h"
@@ -334,6 +335,11 @@ class DBusServices {
         CrosDBusService::CreateServiceProviderList(
             std::make_unique<KioskInfoService>()));
 
+    metrics_event_service_ = CrosDBusService::Create(
+        kMetricsEventServiceName, dbus::ObjectPath(kMetricsEventServicePath),
+        CrosDBusService::CreateServiceProviderList(
+            std::make_unique<MetricsEventServiceProvider>()));
+
     screen_lock_service_ = CrosDBusService::Create(
         kScreenLockServiceName, dbus::ObjectPath(kScreenLockServicePath),
         CrosDBusService::CreateServiceProviderList(
@@ -407,6 +413,7 @@ class DBusServices {
     TPMTokenLoader::Shutdown();
     proxy_resolution_service_.reset();
     kiosk_info_service_.reset();
+    metrics_event_service_.reset();
     virtual_file_request_service_.reset();
     component_updater_service_.reset();
     chrome_features_service_.reset();
@@ -423,6 +430,7 @@ class DBusServices {
  private:
   std::unique_ptr<CrosDBusService> proxy_resolution_service_;
   std::unique_ptr<CrosDBusService> kiosk_info_service_;
+  std::unique_ptr<CrosDBusService> metrics_event_service_;
   std::unique_ptr<CrosDBusService> screen_lock_service_;
   std::unique_ptr<CrosDBusService> virtual_file_request_service_;
   std::unique_ptr<CrosDBusService> component_updater_service_;

chrome/browser/chromeos/dbus/metrics_event_service_provider.cc

+// Copyright 2018 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/chromeos/dbus/metrics_event_service_provider.h"
+
+#include <time.h>
+
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/resource_coordinator/tab_manager.h"
+#include "dbus/message.h"
+#include "third_party/cros_system_api/dbus/service_constants.h"
+
+namespace chromeos {
+
+MetricsEventServiceProvider::MetricsEventServiceProvider() {}
+
+MetricsEventServiceProvider::~MetricsEventServiceProvider() {
+  DCHECK(g_browser_process);
+  if (exported_object_)
+    g_browser_process->GetTabManager()->RemoveObserver(this);
+}
+
+void MetricsEventServiceProvider::Start(
+    scoped_refptr<dbus::ExportedObject> exported_object) {
+  exported_object_ = exported_object;
+  DCHECK(g_browser_process);
+  g_browser_process->GetTabManager()->AddObserver(this);
+}
+
+void MetricsEventServiceProvider::OnDiscardedStateChange(
+    content::WebContents* contents,
+    bool is_discarded) {
+  if (is_discarded) {
+    EmitSignal(metrics_event::Event_Type_TAB_DISCARD);
+  }
+}
+
+void MetricsEventServiceProvider::EmitSignal(metrics_event::Event_Type type) {
+  DCHECK(exported_object_);
+
+  dbus::Signal signal(chromeos::kMetricsEventServiceInterface,
+                      chromeos::kMetricsEventServiceChromeEventSignal);
+  metrics_event::Event payload;
+
+  // Here we have a Chrome/Chrome OS specific agreement to use clock_gettime
+  // with CLOCK_MONOTONIC.
+  struct timespec timespec;
+  // clock_gettime() can only fail on bad pointer, or bad clock specifier, so
+  // the following call "cannot" fail.
+  int ret = clock_gettime(CLOCK_MONOTONIC, &timespec);
+  if (ret != 0) {
+    PLOG(DFATAL) << "clock_gettime";
+    return;
+  }
+  int64_t now_ms = timespec.tv_sec * 1000 + timespec.tv_nsec / (1000 * 1000);
+
+  dbus::MessageWriter writer(&signal);
+  payload.set_type(type);
+  payload.set_timestamp(now_ms);
+  dbus::MessageWriter(&signal).AppendProtoAsArrayOfBytes(payload);
+  exported_object_->SendSignal(&signal);
+}
+
+}  // namespace chromeos

chrome/browser/chromeos/dbus/metrics_event_service_provider.h

+// Copyright 2018 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 CHROME_BROWSER_CHROMEOS_DBUS_METRICS_EVENT_SERVICE_PROVIDER_H_
+#define CHROME_BROWSER_CHROMEOS_DBUS_METRICS_EVENT_SERVICE_PROVIDER_H_
+
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "chrome/browser/resource_coordinator/tab_lifecycle_observer.h"
+#include "chromeos/dbus/metrics_event/metrics_event.pb.h"
+#include "chromeos/dbus/services/cros_dbus_service.h"
+#include "dbus/exported_object.h"
+
+namespace chromeos {
+
+// This class does not export any methods.  An instance of this class can send
+// signals to clients for a number of events of statistical interest, e.g. tab
+// discards.
+class MetricsEventServiceProvider
+    : public CrosDBusService::ServiceProviderInterface,
+      public resource_coordinator::TabLifecycleObserver {
+ public:
+  MetricsEventServiceProvider();
+  ~MetricsEventServiceProvider() override;
+
+  // CrosDBusService::ServiceProviderInterface overrides:
+  void Start(scoped_refptr<dbus::ExportedObject> exported_object) override;
+
+ private:
+  // resource_coordinator::TabLifecycleObserver:
+  void OnDiscardedStateChange(content::WebContents* contents,
+                              bool is_discarded) override;
+  void OnAutoDiscardableStateChange(content::WebContents* contents,
+                                    bool is_auto_discardable) override {}
+
+  // Emits the D-Bus signal for this event.
+  void EmitSignal(metrics_event::Event_Type type);
+
+  // A reference on ExportedObject for sending signals.
+  scoped_refptr<dbus::ExportedObject> exported_object_;
+
+  DISALLOW_COPY_AND_ASSIGN(MetricsEventServiceProvider);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_DBUS_METRICS_EVENT_SERVICE_PROVIDER_H_

chrome/browser/chromeos/dbus/org.chromium.MetricsEventService.conf

+<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
+  "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
+<!--
+  Copyright (c) 2018 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.
+
+  This file will be installed at /opt/google/chrome/dbus on Chromium OS.
+-->
+<busconfig>
+  <policy user="chronos">
+    <allow own="org.chromium.MetricsEventService"/>
+  </policy>
+</busconfig>

chromeos/BUILD.gn

@@ -30,6 +30,7 @@ component("chromeos") {
     ":cryptohome_proto",
     ":login_manager_proto",
     ":media_perception_proto",
+    ":metrics_event_proto",
     ":power_manager_proto",
     ":seneschal_proto",
     ":smbprovider_proto",
@@ -880,6 +881,14 @@ proto_library("power_manager_proto") {
   proto_out_dir = "chromeos/dbus/power_manager"
 }
 
+proto_library("metrics_event_proto") {
+  sources = [
+    "//third_party/cros_system_api/dbus/metrics_event/metrics_event.proto",
+  ]
+
+  proto_out_dir = "chromeos/dbus/metrics_event"
+}
+
 proto_library("attestation_proto") {
   sources = [
     "dbus/proto/attestation.proto",