Factor management of metrics updates into its own class.

chrome/browser/page_load_metrics/page_load_metrics_update_dispatcher.cc

-// Copyright 2016 The Chromium Authors. All rights reserved.
+// Copyright 2017 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/page_load_metrics/page_load_tracker.h"
+#include "chrome/browser/page_load_metrics/page_load_metrics_update_dispatcher.h"
 
-#include <algorithm>
-#include <ostream>

[Charlie Harrison, 2017/05/24 21:02:51]

shouldn't be removed

[Bryan McQuade, 2017/05/25 02:30:21]

done

-#include <string>
 #include <utility>
 
-#include "base/logging.h"

[Charlie Harrison, 2017/05/24 21:02:51]

shouldn't be removed

[Bryan McQuade, 2017/05/25 02:30:21]

done

-#include "base/memory/ptr_util.h"
-#include "base/metrics/histogram_macros.h"

[Charlie Harrison, 2017/05/24 21:02:51]

We're still using UMA_HISTOGRAM_ENUMERATION

[Bryan McQuade, 2017/05/25 02:30:21]

done

 #include "chrome/browser/page_load_metrics/browser_page_track_decider.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_embedder_interface.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_util.h"
-#include "chrome/browser/prerender/prerender_contents.h"
-#include "chrome/common/page_load_metrics/page_load_timing.h"
-#include "content/public/browser/navigation_details.h"
+#include "chrome/browser/page_load_metrics/page_load_tracker.h"
+#include "chrome/common/page_load_metrics/page_load_metrics_util.h"
 #include "content/public/browser/navigation_handle.h"
 #include "content/public/browser/render_frame_host.h"
-#include "content/public/browser/web_contents.h"
-#include "content/public/browser/web_contents_observer.h"
-#include "content/public/common/browser_side_navigation_policy.h"
-#include "ui/base/page_transition_types.h"
-
-// This macro invokes the specified method on each observer, passing the
-// variable length arguments as the method's arguments, and removes the observer
-// from the list of observers if the given method returns STOP_OBSERVING.
-#define INVOKE_AND_PRUNE_OBSERVERS(observers, Method, ...)    \
-  for (auto it = observers.begin(); it != observers.end();) { \
-    if ((*it)->Method(__VA_ARGS__) ==                         \
-        PageLoadMetricsObserver::STOP_OBSERVING) {            \
-      it = observers.erase(it);                               \
-    } else {                                                  \
-      ++it;                                                   \
-    }                                                         \
-  }
 
 namespace page_load_metrics {
 
 namespace internal {
 
-const char kErrorEvents[] = "PageLoad.Internal.ErrorCode";
-const char kAbortChainSizeReload[] =
-    "PageLoad.Internal.ProvisionalAbortChainSize.Reload";
-const char kAbortChainSizeForwardBack[] =
-    "PageLoad.Internal.ProvisionalAbortChainSize.ForwardBack";
-const char kAbortChainSizeNewNavigation[] =
-    "PageLoad.Internal.ProvisionalAbortChainSize.NewNavigation";
-const char kAbortChainSizeSameURL[] =
-    "PageLoad.Internal.ProvisionalAbortChainSize.SameURL";
-const char kAbortChainSizeNoCommit[] =
-    "PageLoad.Internal.ProvisionalAbortChainSize.NoCommit";
-const char kClientRedirectFirstPaintToNavigation[] =
-    "PageLoad.Internal.ClientRedirect.FirstPaintToNavigation";
-const char kClientRedirectWithoutPaint[] =
-    "PageLoad.Internal.ClientRedirect.NavigationWithoutPaint";
-const char kPageLoadCompletedAfterAppBackground[] =
-    "PageLoad.Internal.PageLoadCompleted.AfterAppBackground";
-const char kPageLoadStartedInForeground[] =
-    "PageLoad.Internal.NavigationStartedInForeground";
-const char kPageLoadPrerender[] = "PageLoad.Internal.Prerender";
 const char kPageLoadTimingStatus[] = "PageLoad.Internal.PageLoadTimingStatus";
 const char kPageLoadTimingDispatchStatus[] =
     "PageLoad.Internal.PageLoadTimingStatus.AtTimingCallbackDispatch";
 
 }  // namespace internal
 
-void RecordInternalError(InternalErrorLoadEvent event) {
-  UMA_HISTOGRAM_ENUMERATION(internal::kErrorEvents, event, ERR_LAST_ENTRY);
-}
-
-// TODO(csharrison): Add a case for client side redirects, which is what JS
-// initiated window.location / window.history navigations get set to.
-PageEndReason EndReasonForPageTransition(ui::PageTransition transition) {
-  if (transition & ui::PAGE_TRANSITION_CLIENT_REDIRECT) {
-    return END_CLIENT_REDIRECT;
-  }
-  if (ui::PageTransitionCoreTypeIs(transition, ui::PAGE_TRANSITION_RELOAD))
-    return END_RELOAD;
-  if (transition & ui::PAGE_TRANSITION_FORWARD_BACK)
-    return END_FORWARD_BACK;
-  if (ui::PageTransitionIsNewNavigation(transition))
-    return END_NEW_NAVIGATION;
-  NOTREACHED()
-      << "EndReasonForPageTransition received unexpected ui::PageTransition: "
-      << transition;
-  return END_OTHER;
-}
-
-void LogAbortChainSameURLHistogram(int aborted_chain_size_same_url) {
-  if (aborted_chain_size_same_url > 0) {
-    UMA_HISTOGRAM_COUNTS(internal::kAbortChainSizeSameURL,
-                         aborted_chain_size_same_url);
-  }
-}
-
-bool IsNavigationUserInitiated(content::NavigationHandle* handle) {
-  // TODO(crbug.com/617904): Browser initiated navigations should have
-  // HasUserGesture() set to true. In the meantime, we consider all
-  // browser-initiated navigations to be user initiated.
-  //
-  // TODO(crbug.com/637345): Some browser-initiated navigations incorrectly
-  // report that they are renderer-initiated. We will currently report that
-  // these navigations are not user initiated, when in fact they are user
-  // initiated.
-  return handle->HasUserGesture() || !handle->IsRendererInitiated();
-}
-
 namespace {
 
 // Helper to allow use of Optional<> values in LOG() messages.
 std::ostream& operator<<(std::ostream& os,
                          const base::Optional<base::TimeDelta>& opt) {

[Charlie Harrison, 2017/05/24 21:02:51]

include optional

   if (opt)
     os << opt.value();
   else
     os << "(unset)";
   return os;
 }
 
 // If second is non-zero, first must also be non-zero and less than or equal to
 // second.
 bool EventsInOrder(const base::Optional<base::TimeDelta>& first,
@@ skipping 182 matching lines @@
     // occasionally, as inter-frame updates can arrive out of order. Record a
     // histogram to track how frequently it happens, along with the magnitude
     // of the delta.
     PAGE_LOAD_HISTOGRAM("PageLoad.Internal.OutOfOrderInterFrameTiming",
                         inout_existing_value->value() - candidate_new_value);
   }
 
   *inout_existing_value = candidate_new_value;
 }
 
-void RecordAppBackgroundPageLoadCompleted(bool completed_after_background) {
-  UMA_HISTOGRAM_BOOLEAN(internal::kPageLoadCompletedAfterAppBackground,
-                        completed_after_background);
-}
-
-void DispatchObserverTimingCallbacks(
-    PageLoadMetricsObserver* observer,
-    const mojom::PageLoadTiming& last_timing,
-    const mojom::PageLoadTiming& new_timing,
-    const mojom::PageLoadMetadata& last_metadata,
-    const PageLoadExtraInfo& extra_info) {
-  if (extra_info.main_frame_metadata.behavior_flags !=
-      last_metadata.behavior_flags)
-    observer->OnLoadingBehaviorObserved(extra_info);
-  if (!last_timing.Equals(new_timing))
-    observer->OnTimingUpdate(new_timing, extra_info);
-  if (new_timing.document_timing->dom_content_loaded_event_start &&
-      !last_timing.document_timing->dom_content_loaded_event_start)
-    observer->OnDomContentLoadedEventStart(new_timing, extra_info);
-  if (new_timing.document_timing->load_event_start &&
-      !last_timing.document_timing->load_event_start)
-    observer->OnLoadEventStart(new_timing, extra_info);
-  if (new_timing.document_timing->first_layout &&
-      !last_timing.document_timing->first_layout)
-    observer->OnFirstLayout(new_timing, extra_info);
-  if (new_timing.paint_timing->first_paint &&
-      !last_timing.paint_timing->first_paint)
-    observer->OnFirstPaintInPage(new_timing, extra_info);
-  if (new_timing.paint_timing->first_text_paint &&
-      !last_timing.paint_timing->first_text_paint)
-    observer->OnFirstTextPaintInPage(new_timing, extra_info);
-  if (new_timing.paint_timing->first_image_paint &&
-      !last_timing.paint_timing->first_image_paint)
-    observer->OnFirstImagePaintInPage(new_timing, extra_info);
-  if (new_timing.paint_timing->first_contentful_paint &&
-      !last_timing.paint_timing->first_contentful_paint)
-    observer->OnFirstContentfulPaintInPage(new_timing, extra_info);
-  if (new_timing.paint_timing->first_meaningful_paint &&
-      !last_timing.paint_timing->first_meaningful_paint)
-    observer->OnFirstMeaningfulPaintInMainFrameDocument(new_timing, extra_info);
-  if (new_timing.parse_timing->parse_start &&
-      !last_timing.parse_timing->parse_start)
-    observer->OnParseStart(new_timing, extra_info);
-  if (new_timing.parse_timing->parse_stop &&
-      !last_timing.parse_timing->parse_stop)
-    observer->OnParseStop(new_timing, extra_info);
-}
-
 }  // namespace
 
-PageLoadTracker::PageLoadTracker(
-    bool in_foreground,
-    PageLoadMetricsEmbedderInterface* embedder_interface,
-    const GURL& currently_committed_url,
+PageLoadMetricsUpdateDispatcher::PageLoadMetricsUpdateDispatcher(
+    PageLoadMetricsUpdateDispatcher::Client* client,
     content::NavigationHandle* navigation_handle,
-    UserInitiatedInfo user_initiated_info,
-    int aborted_chain_size,
-    int aborted_chain_size_same_url)
-    : did_stop_tracking_(false),
-      app_entered_background_(false),
+    PageLoadMetricsEmbedderInterface* embedder_interface)
+    : client_(client),
+      embedder_interface_(embedder_interface),
       navigation_start_(navigation_handle->NavigationStart()),
-      url_(navigation_handle->GetURL()),
-      start_url_(navigation_handle->GetURL()),
-      did_commit_(false),
-      page_end_reason_(END_NONE),
-      page_end_user_initiated_info_(UserInitiatedInfo::NotUserInitiated()),
-      started_in_foreground_(in_foreground),
-      merged_page_timing_(CreatePageLoadTiming()),
-      last_dispatched_merged_page_timing_(CreatePageLoadTiming()),
-      last_dispatched_main_frame_metadata_(mojom::PageLoadMetadata::New()),
-      page_transition_(navigation_handle->GetPageTransition()),
-      user_initiated_info_(user_initiated_info),
-      aborted_chain_size_(aborted_chain_size),
-      aborted_chain_size_same_url_(aborted_chain_size_same_url),
-      embedder_interface_(embedder_interface) {
-  DCHECK(!navigation_handle->HasCommitted());
-  embedder_interface_->RegisterObservers(this);
-  INVOKE_AND_PRUNE_OBSERVERS(observers_, OnStart, navigation_handle,
-                             currently_committed_url, started_in_foreground_);
+      current_merged_page_timing_(CreatePageLoadTiming()),
+      pending_merged_page_timing_(CreatePageLoadTiming()),
+      main_frame_metadata_(mojom::PageLoadMetadata::New()),
+      subframe_metadata_(mojom::PageLoadMetadata::New()) {}
 
-  UMA_HISTOGRAM_BOOLEAN(internal::kPageLoadStartedInForeground,
-                        started_in_foreground_);
-  const bool is_prerender = prerender::PrerenderContents::FromWebContents(
-                                navigation_handle->GetWebContents()) != nullptr;
-  if (is_prerender) {
-    UMA_HISTOGRAM_BOOLEAN(internal::kPageLoadPrerender, true);
+PageLoadMetricsUpdateDispatcher::~PageLoadMetricsUpdateDispatcher() {}
+
+void PageLoadMetricsUpdateDispatcher::UpdateMetrics(
+    content::RenderFrameHost* render_frame_host,
+    const mojom::PageLoadTiming& new_timing,
+    const mojom::PageLoadMetadata& new_metadata) {
+  if (render_frame_host->GetParent() == nullptr) {
+    UpdateMainFrameMetadata(new_metadata);
+    UpdateMainFrameTiming(new_timing);
+  } else {
+    UpdateSubFrameMetadata(new_metadata);
+    UpdateSubFrameTiming(render_frame_host, new_timing);
   }
 }
 
-PageLoadTracker::~PageLoadTracker() {
-  if (app_entered_background_) {
-    RecordAppBackgroundPageLoadCompleted(true);
-  }
-
-  if (did_stop_tracking_)
-    return;
-
-  if (page_end_time_.is_null()) {
-    // page_end_time_ can be unset in some cases, such as when a navigation is
-    // aborted by a navigation that started before it. In these cases, set the
-    // end time to the current time.
-    RecordInternalError(ERR_NO_PAGE_LOAD_END_TIME);
-    NotifyPageEnd(END_OTHER, UserInitiatedInfo::NotUserInitiated(),
-                  base::TimeTicks::Now(), true);
-  }
-
-  if (!did_commit_) {
-    if (!failed_provisional_load_info_)
-      RecordInternalError(ERR_NO_COMMIT_OR_FAILED_PROVISIONAL_LOAD);
-
-    // Don't include any aborts that resulted in a new navigation, as the chain
-    // length will be included in the aborter PageLoadTracker.
-    if (page_end_reason_ != END_RELOAD &&
-        page_end_reason_ != END_FORWARD_BACK &&
-        page_end_reason_ != END_NEW_NAVIGATION) {
-      LogAbortChainHistograms(nullptr);
-    }
-  } else if (page_load_metrics::IsEmpty(*merged_page_timing_)) {
-    RecordInternalError(ERR_NO_IPCS_RECEIVED);
-  }
-
-  const PageLoadExtraInfo info = ComputePageLoadExtraInfo();
-  for (const auto& observer : observers_) {
-    if (failed_provisional_load_info_) {
-      observer->OnFailedProvisionalLoad(*failed_provisional_load_info_, info);
-    } else if (did_commit_) {
-      observer->OnComplete(*merged_page_timing_, info);
-    }
-  }
-}
-
-void PageLoadTracker::LogAbortChainHistograms(
-    content::NavigationHandle* final_navigation) {
-  if (aborted_chain_size_ == 0)
-    return;
-  // Note that this could be broken out by this navigation's abort type, if more
-  // granularity is needed. Add one to the chain size to count the current
-  // navigation. In the other cases, the current navigation is the final
-  // navigation (which commits).
-  if (!final_navigation) {
-    UMA_HISTOGRAM_COUNTS(internal::kAbortChainSizeNoCommit,
-                         aborted_chain_size_ + 1);
-    LogAbortChainSameURLHistogram(aborted_chain_size_same_url_ + 1);
-    return;
-  }
-
-  // The following is only executed for committing trackers.
-  DCHECK(did_commit_);
-
-  // Note that histograms could be separated out by this commit's transition
-  // type, but for simplicity they will all be bucketed together.
-  LogAbortChainSameURLHistogram(aborted_chain_size_same_url_);
-
-  ui::PageTransition committed_transition =
-      final_navigation->GetPageTransition();
-  switch (EndReasonForPageTransition(committed_transition)) {
-    case END_RELOAD:
-      UMA_HISTOGRAM_COUNTS(internal::kAbortChainSizeReload,
-                           aborted_chain_size_);
-      return;
-    case END_FORWARD_BACK:
-      UMA_HISTOGRAM_COUNTS(internal::kAbortChainSizeForwardBack,
-                           aborted_chain_size_);
-      return;
-    // TODO(csharrison): Refactor this code so it is based on the WillStart*
-    // code path instead of the committed load code path. Then, for every abort
-    // chain, log a histogram of the counts of each of these metrics. For now,
-    // merge client redirects with new navigations, which was (basically) the
-    // previous behavior.
-    case END_CLIENT_REDIRECT:
-    case END_NEW_NAVIGATION:
-      UMA_HISTOGRAM_COUNTS(internal::kAbortChainSizeNewNavigation,
-                           aborted_chain_size_);
-      return;
-    default:
-      NOTREACHED()
-          << "LogAbortChainHistograms received unexpected ui::PageTransition: "
-          << committed_transition;
-      return;
-  }
-}
-
-void PageLoadTracker::WebContentsHidden() {
-  // Only log the first time we background in a given page load.
-  if (background_time_.is_null()) {
-    // Make sure we either started in the foreground and haven't been
-    // foregrounded yet, or started in the background and have already been
-    // foregrounded.
-    DCHECK_EQ(started_in_foreground_, foreground_time_.is_null());
-    background_time_ = base::TimeTicks::Now();
-    ClampBrowserTimestampIfInterProcessTimeTickSkew(&background_time_);
-  }
-  const PageLoadExtraInfo info = ComputePageLoadExtraInfo();
-  INVOKE_AND_PRUNE_OBSERVERS(observers_, OnHidden, *merged_page_timing_, info);
-}
-
-void PageLoadTracker::WebContentsShown() {
-  // Only log the first time we foreground in a given page load.
-  if (foreground_time_.is_null()) {
-    // Make sure we either started in the background and haven't been
-    // backgrounded yet, or started in the foreground and have already been
-    // backgrounded.
-    DCHECK_NE(started_in_foreground_, background_time_.is_null());
-    foreground_time_ = base::TimeTicks::Now();
-    ClampBrowserTimestampIfInterProcessTimeTickSkew(&foreground_time_);
-  }
-
-  INVOKE_AND_PRUNE_OBSERVERS(observers_, OnShown);
-}
-
-void PageLoadTracker::WillProcessNavigationResponse(
+void PageLoadMetricsUpdateDispatcher::DidFinishSubFrameNavigation(
     content::NavigationHandle* navigation_handle) {
-  DCHECK(!navigation_request_id_.has_value());
-  navigation_request_id_ = navigation_handle->GetGlobalRequestID();
-  DCHECK(navigation_request_id_.value() != content::GlobalRequestID());
-}
-
-void PageLoadTracker::Commit(content::NavigationHandle* navigation_handle) {
-  did_commit_ = true;
-  url_ = navigation_handle->GetURL();
-  // Some transitions (like CLIENT_REDIRECT) are only known at commit time.
-  page_transition_ = navigation_handle->GetPageTransition();
-  user_initiated_info_.user_gesture = navigation_handle->HasUserGesture();
-
-  INVOKE_AND_PRUNE_OBSERVERS(
-      observers_, ShouldObserveMimeType,
-      navigation_handle->GetWebContents()->GetContentsMimeType());
-
-  INVOKE_AND_PRUNE_OBSERVERS(observers_, OnCommit, navigation_handle);
-  LogAbortChainHistograms(navigation_handle);
-}
-
-void PageLoadTracker::DidCommitSameDocumentNavigation(
-    content::NavigationHandle* navigation_handle) {
-  for (const auto& observer : observers_) {
-    observer->OnCommitSameDocumentNavigation(navigation_handle);
-  }
-}
-
-void PageLoadTracker::DidFinishSubFrameNavigation(
-    content::NavigationHandle* navigation_handle) {
-  for (const auto& observer : observers_) {
-    observer->OnDidFinishSubFrameNavigation(navigation_handle);
-  }
-
   if (!navigation_handle->HasCommitted())
     return;
 
   // We have a new committed navigation, so discard information about the
   // previously committed navigation.
   subframe_navigation_start_offset_.erase(
       navigation_handle->GetFrameTreeNodeId());
 
   BrowserPageTrackDecider decider(embedder_interface_,
                                   navigation_handle->GetWebContents(),
                                   navigation_handle);
   if (!decider.ShouldTrack())
     return;
 
   if (navigation_start_ > navigation_handle->NavigationStart()) {
     RecordInternalError(ERR_SUBFRAME_NAVIGATION_START_BEFORE_MAIN_FRAME);
     return;
   }
   base::TimeDelta navigation_delta =
       navigation_handle->NavigationStart() - navigation_start_;
   subframe_navigation_start_offset_.insert(std::make_pair(
       navigation_handle->GetFrameTreeNodeId(), navigation_delta));
 }
 
-void PageLoadTracker::FailedProvisionalLoad(
-    content::NavigationHandle* navigation_handle,
-    base::TimeTicks failed_load_time) {
-  DCHECK(!failed_provisional_load_info_);
-  failed_provisional_load_info_.reset(new FailedProvisionalLoadInfo(
-      failed_load_time - navigation_handle->NavigationStart(),
-      navigation_handle->GetNetErrorCode()));
-}
-
-void PageLoadTracker::Redirect(content::NavigationHandle* navigation_handle) {
-  url_ = navigation_handle->GetURL();
-  INVOKE_AND_PRUNE_OBSERVERS(observers_, OnRedirect, navigation_handle);
-}
-
-void PageLoadTracker::OnInputEvent(const blink::WebInputEvent& event) {
-  input_tracker_.OnInputEvent(event);
-  for (const auto& observer : observers_) {
-    observer->OnUserInput(event);
-  }
-}
-
-void PageLoadTracker::FlushMetricsOnAppEnterBackground() {
-  if (!app_entered_background_) {
-    RecordAppBackgroundPageLoadCompleted(false);
-    app_entered_background_ = true;
-  }
-
-  const PageLoadExtraInfo info = ComputePageLoadExtraInfo();
-  INVOKE_AND_PRUNE_OBSERVERS(observers_, FlushMetricsOnAppEnterBackground,
-                             *merged_page_timing_, info);
-}
-
-void PageLoadTracker::NotifyClientRedirectTo(
-    const PageLoadTracker& destination) {
-  if (merged_page_timing_->paint_timing->first_paint) {
-    base::TimeTicks first_paint_time =
-        navigation_start() +
-        merged_page_timing_->paint_timing->first_paint.value();
-    base::TimeDelta first_paint_to_navigation;
-    if (destination.navigation_start() > first_paint_time)
-      first_paint_to_navigation =
-          destination.navigation_start() - first_paint_time;
-    PAGE_LOAD_HISTOGRAM(internal::kClientRedirectFirstPaintToNavigation,
-                        first_paint_to_navigation);
-  } else {
-    UMA_HISTOGRAM_BOOLEAN(internal::kClientRedirectWithoutPaint, true);
-  }
-}
-
-void PageLoadTracker::UpdateSubFrameTiming(
+void PageLoadMetricsUpdateDispatcher::UpdateSubFrameTiming(
     content::RenderFrameHost* render_frame_host,
-    const mojom::PageLoadTiming& new_timing,
-    const mojom::PageLoadMetadata& new_metadata) {
-  UpdateSubFrameMetadata(new_metadata);
+    const mojom::PageLoadTiming& new_timing) {
   const auto it = subframe_navigation_start_offset_.find(
       render_frame_host->GetFrameTreeNodeId());
   if (it == subframe_navigation_start_offset_.end()) {
     // We received timing information for an untracked load. Ignore it.
     return;
   }
 
   base::TimeDelta navigation_start_offset = it->second;
   MergePaintTiming(navigation_start_offset, *(new_timing.paint_timing),
                    false /* is_main_frame */);
 
   DispatchTimingUpdates();
 }
 
-void PageLoadTracker::MergePaintTiming(
+void PageLoadMetricsUpdateDispatcher::MergePaintTiming(
     base::TimeDelta navigation_start_offset,
     const mojom::PaintTiming& new_paint_timing,
     bool is_main_frame) {
-  MaybeUpdateTimeDelta(&merged_page_timing_->paint_timing->first_paint,
+  MaybeUpdateTimeDelta(&pending_merged_page_timing_->paint_timing->first_paint,
                        navigation_start_offset, new_paint_timing.first_paint);
-  MaybeUpdateTimeDelta(&merged_page_timing_->paint_timing->first_text_paint,
-                       navigation_start_offset,
-                       new_paint_timing.first_text_paint);
-  MaybeUpdateTimeDelta(&merged_page_timing_->paint_timing->first_image_paint,
-                       navigation_start_offset,
-                       new_paint_timing.first_image_paint);
   MaybeUpdateTimeDelta(
-      &merged_page_timing_->paint_timing->first_contentful_paint,
+      &pending_merged_page_timing_->paint_timing->first_text_paint,
+      navigation_start_offset, new_paint_timing.first_text_paint);
+  MaybeUpdateTimeDelta(
+      &pending_merged_page_timing_->paint_timing->first_image_paint,
+      navigation_start_offset, new_paint_timing.first_image_paint);
+  MaybeUpdateTimeDelta(
+      &pending_merged_page_timing_->paint_timing->first_contentful_paint,
       navigation_start_offset, new_paint_timing.first_contentful_paint);
   if (is_main_frame) {
     // first meaningful paint is only tracked in the main frame.
-    merged_page_timing_->paint_timing->first_meaningful_paint =
+    pending_merged_page_timing_->paint_timing->first_meaningful_paint =
         new_paint_timing.first_meaningful_paint;
   }
 }
 
-void PageLoadTracker::UpdateSubFrameMetadata(
+void PageLoadMetricsUpdateDispatcher::UpdateSubFrameMetadata(
     const mojom::PageLoadMetadata& subframe_metadata) {
   // Merge the subframe loading behavior flags with any we've already observed,
   // possibly from other subframes.
   const int last_subframe_loading_behavior_flags =
-      subframe_metadata_.behavior_flags;
-  subframe_metadata_.behavior_flags |= subframe_metadata.behavior_flags;
-  if (last_subframe_loading_behavior_flags == subframe_metadata_.behavior_flags)
+      subframe_metadata_->behavior_flags;
+  subframe_metadata_->behavior_flags |= subframe_metadata.behavior_flags;
+  if (last_subframe_loading_behavior_flags ==
+      subframe_metadata_->behavior_flags)
     return;
 
-  PageLoadExtraInfo extra_info(ComputePageLoadExtraInfo());
-  for (const auto& observer : observers_) {
-    observer->OnLoadingBehaviorObserved(extra_info);
-  }
+  client_->OnSubframeMetadataChanged();
 }
 
-void PageLoadTracker::UpdateTiming(
-    const mojom::PageLoadTiming& new_timing,
-    const mojom::PageLoadMetadata& new_metadata) {
+void PageLoadMetricsUpdateDispatcher::UpdateMainFrameTiming(
+    const mojom::PageLoadTiming& new_timing) {
   // Throw away IPCs that are not relevant to the current navigation.
   // Two timing structures cannot refer to the same navigation if they indicate
   // that a navigation started at different times, so a new timing struct with a
   // different start time from an earlier struct is considered invalid.
   const bool valid_timing_descendent =
-      merged_page_timing_->navigation_start.is_null() ||
-      merged_page_timing_->navigation_start == new_timing.navigation_start;
+      pending_merged_page_timing_->navigation_start.is_null() ||
+      pending_merged_page_timing_->navigation_start ==
+          new_timing.navigation_start;
   if (!valid_timing_descendent) {
     RecordInternalError(ERR_BAD_TIMING_IPC_INVALID_TIMING_DESCENDENT);
     return;
   }
 
-  // Ensure flags sent previously are still present in the new metadata fields.
-  const bool valid_behavior_descendent =
-      (main_frame_metadata_.behavior_flags & new_metadata.behavior_flags) ==
-      main_frame_metadata_.behavior_flags;
-  if (!valid_behavior_descendent) {
-    RecordInternalError(ERR_BAD_TIMING_IPC_INVALID_BEHAVIOR_DESCENDENT);
-    return;
-  }
   internal::PageLoadTimingStatus status = IsValidPageLoadTiming(new_timing);
   UMA_HISTOGRAM_ENUMERATION(internal::kPageLoadTimingStatus, status,
                             internal::LAST_PAGE_LOAD_TIMING_STATUS);
   if (status != internal::VALID) {
     RecordInternalError(ERR_BAD_TIMING_IPC_INVALID_TIMING);
     return;
   }
 
-  DCHECK(did_commit_);  // OnCommit() must be called first.
-  // There are some subtle ordering constraints here. GetPageLoadMetricsInfo()
-  // must be called before DispatchObserverTimingCallbacks, but its
-  // implementation depends on the state of main_frame_metadata_, so we need
-  // to update main_frame_metadata_ before calling GetPageLoadMetricsInfo.
-  // Thus, we make a copy of timing here, update merged_page_timing_ and
-  // main_frame_metadata_, and then proceed to dispatch the observer timing
-  // callbacks.
-  const mojom::PaintTimingPtr last_paint_timing =
-      std::move(merged_page_timing_->paint_timing);
-
-  // Update the merged_page_timing_, making sure to merge the previously
+  mojom::PaintTimingPtr last_paint_timing =
+      std::move(pending_merged_page_timing_->paint_timing);
+  // Update the pending_merged_page_timing_, making sure to merge the previously
   // observed |paint_timing|, which is tracked across all frames in the page.
-  merged_page_timing_ = new_timing.Clone();
-  merged_page_timing_->paint_timing = last_paint_timing.Clone();
+  pending_merged_page_timing_ = new_timing.Clone();
+  pending_merged_page_timing_->paint_timing = std::move(last_paint_timing);
   MergePaintTiming(base::TimeDelta(), *new_timing.paint_timing,
                    true /* is_main_frame */);
 
-  main_frame_metadata_ = new_metadata;
-
   DispatchTimingUpdates();
 }
 
-void PageLoadTracker::DispatchTimingUpdates() {
-  if (last_dispatched_merged_page_timing_->Equals(*merged_page_timing_) &&
-      last_dispatched_main_frame_metadata_->Equals(main_frame_metadata_)) {
+void PageLoadMetricsUpdateDispatcher::UpdateMainFrameMetadata(
+    const mojom::PageLoadMetadata& new_metadata) {
+  if (main_frame_metadata_->Equals(new_metadata))
+    return;
+
+  // Ensure flags sent previously are still present in the new metadata fields.
+  const bool valid_behavior_descendent =
+      (main_frame_metadata_->behavior_flags & new_metadata.behavior_flags) ==
+      main_frame_metadata_->behavior_flags;
+  if (!valid_behavior_descendent) {
+    RecordInternalError(ERR_BAD_TIMING_IPC_INVALID_BEHAVIOR_DESCENDENT);
     return;
   }
 
-  if (merged_page_timing_->paint_timing->first_paint) {
-    if (!merged_page_timing_->parse_timing->parse_start ||
-        !merged_page_timing_->document_timing->first_layout) {
+  main_frame_metadata_ = new_metadata.Clone();
+  client_->OnMainFrameMetadataChanged();
+}
+
+void PageLoadMetricsUpdateDispatcher::DispatchTimingUpdates() {
+  if (pending_merged_page_timing_->paint_timing->first_paint) {
+    if (!pending_merged_page_timing_->parse_timing->parse_start ||
+        !pending_merged_page_timing_->document_timing->first_layout) {
       // When merging paint events across frames, we can sometimes encounter
       // cases where we've received a first paint event for a child frame before
       // receiving required earlier events in the main frame, due to buffering
       // in the render process which results in out of order delivery. For
       // example, we may receive a notification for a first paint in a child
       // frame before we've received a notification for parse start or first
       // layout in the main frame. In these cases, we delay sending timing
       // updates until we've received all expected events (e.g. wait to receive
       // a parse or layout event before dispatching a paint event), so observers
       // can make assumptions about ordering of these events in their callbacks.
       return;
     }
   }
 
+  if (current_merged_page_timing_->Equals(*pending_merged_page_timing_))
+    return;
+  current_merged_page_timing_ = pending_merged_page_timing_->Clone();
+
   internal::PageLoadTimingStatus status =
-      IsValidPageLoadTiming(*merged_page_timing_);
+      IsValidPageLoadTiming(*pending_merged_page_timing_);
   UMA_HISTOGRAM_ENUMERATION(internal::kPageLoadTimingDispatchStatus, status,
                             internal::LAST_PAGE_LOAD_TIMING_STATUS);
 
-  const PageLoadExtraInfo info = ComputePageLoadExtraInfo();
-  for (const auto& observer : observers_) {
-    DispatchObserverTimingCallbacks(
-        observer.get(), *last_dispatched_merged_page_timing_,
-        *merged_page_timing_, *last_dispatched_main_frame_metadata_, info);
-  }
-  last_dispatched_merged_page_timing_ = merged_page_timing_->Clone();
-  last_dispatched_main_frame_metadata_ = main_frame_metadata_.Clone();
-}
-
-void PageLoadTracker::OnStartedResource(
-    const ExtraRequestStartInfo& extra_request_start_info) {
-  for (const auto& observer : observers_) {
-    observer->OnStartedResource(extra_request_start_info);
-  }
-}
-
-void PageLoadTracker::OnLoadedResource(
-    const ExtraRequestCompleteInfo& extra_request_complete_info) {
-  for (const auto& observer : observers_) {
-    observer->OnLoadedResource(extra_request_complete_info);
-  }
-}
-
-void PageLoadTracker::StopTracking() {
-  did_stop_tracking_ = true;
-  observers_.clear();
-}
-
-void PageLoadTracker::AddObserver(
-    std::unique_ptr<PageLoadMetricsObserver> observer) {
-  observers_.push_back(std::move(observer));
-}
-
-void PageLoadTracker::ClampBrowserTimestampIfInterProcessTimeTickSkew(
-    base::TimeTicks* event_time) {
-  DCHECK(event_time != nullptr);
-  // Windows 10 GCE bot non-deterministically failed because TimeTicks::Now()
-  // called in the browser process e.g. commit_time was less than
-  // navigation_start_ that was populated in the renderer process because the
-  // clock was not system-wide monotonic.
-  // Note that navigation_start_ can also be set in the browser process in
-  // some cases and in those cases event_time should never be <
-  // navigation_start_. If it is due to a code error and it gets clamped in this
-  // function, on high resolution systems it should lead to a dcheck failure.
-
-  // TODO(shivanisha): Currently IsHighResolution is the best way to check
-  // if the clock is system-wide monotonic. However IsHighResolution
-  // does a broader check to see if the clock in use is high resolution
-  // which also implies it is system-wide monotonic (on Windows).
-  if (base::TimeTicks::IsHighResolution()) {
-    DCHECK(event_time->is_null() || *event_time >= navigation_start_);
-    return;
-  }
-
-  if (!event_time->is_null() && *event_time < navigation_start_) {
-    RecordInternalError(ERR_INTER_PROCESS_TIME_TICK_SKEW);
-    *event_time = navigation_start_;
-  }
-}
-
-PageLoadExtraInfo PageLoadTracker::ComputePageLoadExtraInfo() {
-  base::Optional<base::TimeDelta> first_background_time;
-  base::Optional<base::TimeDelta> first_foreground_time;
-  base::Optional<base::TimeDelta> page_end_time;
-
-  if (!background_time_.is_null()) {
-    DCHECK_GE(background_time_, navigation_start_);
-    first_background_time = background_time_ - navigation_start_;
-  }
-
-  if (!foreground_time_.is_null()) {
-    DCHECK_GE(foreground_time_, navigation_start_);
-    first_foreground_time = foreground_time_ - navigation_start_;
-  }
-
-  if (page_end_reason_ != END_NONE) {
-    DCHECK_GE(page_end_time_, navigation_start_);
-    page_end_time = page_end_time_ - navigation_start_;
-  } else {
-    DCHECK(page_end_time_.is_null());
-  }
-
-  // page_end_reason_ == END_NONE implies page_end_user_initiated_info_ is not
-  // user initiated.
-  DCHECK(page_end_reason_ != END_NONE ||
-         (!page_end_user_initiated_info_.browser_initiated &&
-          !page_end_user_initiated_info_.user_gesture &&
-          !page_end_user_initiated_info_.user_input_event));
-  return PageLoadExtraInfo(
-      navigation_start_, first_background_time, first_foreground_time,
-      started_in_foreground_, user_initiated_info_, url(), start_url_,
-      did_commit_, page_end_reason_, page_end_user_initiated_info_,
-      page_end_time, main_frame_metadata_, subframe_metadata_);
-}
-
-bool PageLoadTracker::HasMatchingNavigationRequestID(
-    const content::GlobalRequestID& request_id) const {
-  DCHECK(request_id != content::GlobalRequestID());
-  return navigation_request_id_.has_value() &&
-         navigation_request_id_.value() == request_id;
-}
-
-void PageLoadTracker::NotifyPageEnd(PageEndReason page_end_reason,
-                                    UserInitiatedInfo user_initiated_info,
-                                    base::TimeTicks timestamp,
-                                    bool is_certainly_browser_timestamp) {
-  DCHECK_NE(page_end_reason, END_NONE);
-  // Use UpdatePageEnd to update an already notified PageLoadTracker.
-  if (page_end_reason_ != END_NONE)
-    return;
-
-  UpdatePageEndInternal(page_end_reason, user_initiated_info, timestamp,
-                        is_certainly_browser_timestamp);
-}
-
-void PageLoadTracker::UpdatePageEnd(PageEndReason page_end_reason,
-                                    UserInitiatedInfo user_initiated_info,
-                                    base::TimeTicks timestamp,
-                                    bool is_certainly_browser_timestamp) {
-  DCHECK_NE(page_end_reason, END_NONE);
-  DCHECK_NE(page_end_reason, END_OTHER);
-  DCHECK_EQ(page_end_reason_, END_OTHER);
-  DCHECK(!page_end_time_.is_null());
-  if (page_end_time_.is_null() || page_end_reason_ != END_OTHER)
-    return;
-
-  // For some aborts (e.g. navigations), the initiated timestamp can be earlier
-  // than the timestamp that aborted the load. Taking the minimum gives the
-  // closest user initiated time known.
-  UpdatePageEndInternal(page_end_reason, user_initiated_info,
-                        std::min(page_end_time_, timestamp),
-                        is_certainly_browser_timestamp);
-}
-
-bool PageLoadTracker::IsLikelyProvisionalAbort(
-    base::TimeTicks abort_cause_time) const {
-  // Note that |abort_cause_time - page_end_time_| can be negative.
-  return page_end_reason_ == END_OTHER &&
-         (abort_cause_time - page_end_time_).InMilliseconds() < 100;
-}
-
-bool PageLoadTracker::MatchesOriginalNavigation(
-    content::NavigationHandle* navigation_handle) {
-  // Neither navigation should have committed.
-  DCHECK(!navigation_handle->HasCommitted());
-  DCHECK(!did_commit_);
-  return navigation_handle->GetURL() == start_url_;
-}
-
-void PageLoadTracker::UpdatePageEndInternal(
-    PageEndReason page_end_reason,
-    UserInitiatedInfo user_initiated_info,
-    base::TimeTicks timestamp,
-    bool is_certainly_browser_timestamp) {
-  // When a provisional navigation commits, that navigation's start time is
-  // interpreted as the abort time for other provisional loads in the tab.
-  // However, this only makes sense if the committed load started after the
-  // aborted provisional loads started. Thus we ignore cases where the committed
-  // load started before the aborted provisional load, as this would result in
-  // recording a negative time-to-abort. The real issue here is that we have to
-  // infer the cause of aborts. It would be better if the navigation code could
-  // instead report the actual cause of an aborted navigation. See crbug/571647
-  // for details.
-  if (timestamp < navigation_start_) {
-    RecordInternalError(ERR_END_BEFORE_NAVIGATION_START);
-    page_end_reason_ = END_NONE;
-    page_end_time_ = base::TimeTicks();
-    return;
-  }
-  page_end_reason_ = page_end_reason;
-  page_end_time_ = timestamp;
-  // A client redirect can never be user initiated. Due to the way Blink
-  // implements user gesture tracking, where all events that occur within 1
-  // second after a user interaction are considered to be triggered by user
-  // activation (based on HTML spec:
-  // https://html.spec.whatwg.org/multipage/interaction.html#triggered-by-user-activation),
-  // these navs may sometimes be reported as user initiated by Blink. Thus, we
-  // explicitly filter these types of aborts out when deciding if the abort was
-  // user initiated.
-  if (page_end_reason != END_CLIENT_REDIRECT)
-    page_end_user_initiated_info_ = user_initiated_info;
-
-  if (is_certainly_browser_timestamp) {
-    ClampBrowserTimestampIfInterProcessTimeTickSkew(&page_end_time_);
-  }
-}
-
-void PageLoadTracker::MediaStartedPlaying(
-    const content::WebContentsObserver::MediaPlayerInfo& video_type,
-    bool is_in_main_frame) {
-  for (const auto& observer : observers_)
-    observer->MediaStartedPlaying(video_type, is_in_main_frame);
-}
-
-void PageLoadTracker::OnNavigationDelayComplete(base::TimeDelta scheduled_delay,
-                                                base::TimeDelta actual_delay) {
-  for (const auto& observer : observers_)
-    observer->OnNavigationDelayComplete(scheduled_delay, actual_delay);
+  client_->OnTimingChanged();
 }
 
 }  // namespace page_load_metrics