Revert "Create and pass shared-histogram-allocator from browser to renderer."

chrome/browser/metrics/subprocess_metrics_provider.cc

-// Copyright 2016 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/metrics/subprocess_metrics_provider.h"
-
-#include "base/logging.h"
-#include "base/memory/ptr_util.h"
-#include "base/metrics/histogram_base.h"
-#include "base/metrics/histogram_macros.h"
-#include "base/metrics/persistent_histogram_allocator.h"
-#include "base/metrics/persistent_memory_allocator.h"
-#include "components/metrics/metrics_service.h"
-#include "content/public/browser/notification_service.h"
-#include "content/public/browser/notification_types.h"
-#include "content/public/browser/render_process_host.h"
-
-SubprocessMetricsProvider::SubprocessMetricsProvider()
-    : scoped_observer_(this) {
-  registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_CREATED,
-                 content::NotificationService::AllBrowserContextsAndSources());
-}
-
-SubprocessMetricsProvider::~SubprocessMetricsProvider() {}
-
-void SubprocessMetricsProvider::RegisterSubprocessAllocator(
-    int id,
-    std::unique_ptr<base::PersistentHistogramAllocator> allocator) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK(!allocators_by_id_.Lookup(id));
-
-  // Map is "MapOwnPointer" so transfer ownership to it.
-  allocators_by_id_.AddWithID(allocator.release(), id);
-}
-
-void SubprocessMetricsProvider::DeregisterSubprocessAllocator(int id) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  if (!allocators_by_id_.Lookup(id))
-    return;
-
-  // Extract the matching allocator from the list of active ones.
-  std::unique_ptr<base::PersistentHistogramAllocator> allocator(
-      allocators_by_id_.Replace(id, nullptr));
-  allocators_by_id_.Remove(id);
-  DCHECK(allocator);
-
-  // If metrics recording is enabled, transfer the allocator to the "release"
-  // list. The allocator will continue to live (and keep the associated shared
-  // memory alive) until the next upload after which it will be released.
-  // Otherwise, the allocator and its memory will be released when the
-  // unique_ptr goes out of scope at the end of this method.
-  if (metrics_recording_enabled_)
-    allocators_to_release_.push_back(std::move(allocator));
-}
-
-void SubprocessMetricsProvider::OnRecordingEnabled() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  metrics_recording_enabled_ = true;
-}
-
-void SubprocessMetricsProvider::OnRecordingDisabled() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  metrics_recording_enabled_ = false;
-  allocators_to_release_.clear();
-}
-
-void SubprocessMetricsProvider::RecordHistogramSnapshotsFromAllocator(
-    base::HistogramSnapshotManager* snapshot_manager,
-    int id,
-    base::PersistentHistogramAllocator* allocator) {
-  DCHECK(allocator);
-
-  int histogram_count = 0;
-  base::PersistentHistogramAllocator::Iterator hist_iter(allocator);
-  while (true) {
-    std::unique_ptr<base::HistogramBase> histogram = hist_iter.GetNext();
-    if (!histogram)
-      break;
-    snapshot_manager->PrepareDeltaTakingOwnership(std::move(histogram));
-    ++histogram_count;
-  }
-
-  DVLOG(1) << "Reported " << histogram_count << " histograms from subprocess #"
-           << id;
-}
-
-void SubprocessMetricsProvider::RecordHistogramSnapshots(
-    base::HistogramSnapshotManager* snapshot_manager) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  for (AllocatorByIdMap::iterator iter(&allocators_by_id_); !iter.IsAtEnd();
-       iter.Advance()) {
-    RecordHistogramSnapshotsFromAllocator(
-        snapshot_manager, iter.GetCurrentKey(), iter.GetCurrentValue());
-  }
-
-  for (auto& allocator : allocators_to_release_)
-    RecordHistogramSnapshotsFromAllocator(snapshot_manager, 0, allocator.get());
-
-  UMA_HISTOGRAM_COUNTS_100(
-      "UMA.SubprocessMetricsProvider.SubprocessCount",
-      allocators_by_id_.size() + allocators_to_release_.size());
-
-  // The snapshot-manager has taken ownership of the histograms but needs
-  // access to only the histogram objects, not "sample" data it uses. Thus,
-  // it is safe to release shared-memory segments without waiting for the
-  // snapshot-manager to "finish".
-  allocators_to_release_.clear();
-}
-
-void SubprocessMetricsProvider::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK_EQ(content::NOTIFICATION_RENDERER_PROCESS_CREATED, type);
-
-  content::RenderProcessHost* host =
-      content::Source<content::RenderProcessHost>(source).ptr();
-
-  // Sometimes, the same host will cause multiple notifications in tests so
-  // could possibly do the same in a release build.
-  if (!scoped_observer_.IsObserving(host))
-    scoped_observer_.Add(host);
-}
-
-void SubprocessMetricsProvider::RenderProcessReady(
-    content::RenderProcessHost* host) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  // If the render-process-host passed a persistent-memory-allocator to the
-  // renderer process, extract it and register it here.
-  std::unique_ptr<base::SharedPersistentMemoryAllocator> allocator =
-      host->TakeMetricsAllocator();
-  if (allocator) {
-    RegisterSubprocessAllocator(
-        host->GetID(),
-        WrapUnique(new base::PersistentHistogramAllocator(
-            std::move(allocator))));
-  }
-}
-
-void SubprocessMetricsProvider::RenderProcessExited(
-    content::RenderProcessHost* host,
-    base::TerminationStatus status,
-    int exit_code) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  DeregisterSubprocessAllocator(host->GetID());
-}
-
-void SubprocessMetricsProvider::RenderProcessHostDestroyed(
-    content::RenderProcessHost* host) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  // It's possible for a Renderer to terminate without RenderProcessExited
-  // (above) being called so it's necessary to de-register also upon the
-  // destruction of the host. If both get called, no harm is done.
-
-  DeregisterSubprocessAllocator(host->GetID());
-  scoped_observer_.Remove(host);
-}