[Tab Metrics] Measure FP, FCP and FMP for Foreground Tab during Session Restore

chrome/browser/page_load_metrics/observers/session_restore_foreground_tab_page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/observers/session_restore_foreground_tab_page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/observers/session_restore_foreground_tab_page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/observers/session_restore_foreground_tab_page_load_metrics_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ef26f331ccc9b1e267537434dff601d158968930
--- /dev/null
+++ b/chrome/browser/page_load_metrics/observers/session_restore_foreground_tab_page_load_metrics_observer.cc
@@ -0,0 +1,72 @@
+// 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/observers/session_restore_foreground_tab_page_load_metrics_observer.h"
+
+#include "base/metrics/histogram_macros.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/resource_coordinator/tab_manager.h"
+
+namespace internal {
+
+const char kHistogramSessionRestoreForegroundTabFirstPaint[] =
+    "TabManager.Experimental.SessionRestore.ForegroundTab.FirstPaint";
+const char kHistogramSessionRestoreForegroundTabFirstContentfulPaint[] =
+    "TabManager.Experimental.SessionRestore.ForegroundTab.FirstContentfulPaint";
+const char kHistogramSessionRestoreForegroundTabFirstMeaningfulPaint[] =
+    "TabManager.Experimental.SessionRestore.ForegroundTab.FirstMeaningfulPaint";
+
+}  // namespace internal
+
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+SessionRestoreForegroundTabPageLoadMetricsObserver::OnStart(
+    content::NavigationHandle* navigation_handle,
+    const GURL& currently_committed_url,
+    bool started_in_foreground) {
+  return (!IsDuringSessionRestore() || !started_in_foreground)
+             ? STOP_OBSERVING
+             : CONTINUE_OBSERVING;
+}
+
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+SessionRestoreForegroundTabPageLoadMetricsObserver::OnHidden(
+    const page_load_metrics::mojom::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  return STOP_OBSERVING;
+}
+
+void SessionRestoreForegroundTabPageLoadMetricsObserver::OnFirstPaintInPage(
+    const page_load_metrics::mojom::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& extra_info) {
+  UMA_HISTOGRAM_TIMES(internal::kHistogramSessionRestoreForegroundTabFirstPaint,
+                      timing.paint_timing->first_paint.value());
+}
+
+void SessionRestoreForegroundTabPageLoadMetricsObserver::
+    OnFirstContentfulPaintInPage(
+        const page_load_metrics::mojom::PageLoadTiming& timing,
+        const page_load_metrics::PageLoadExtraInfo& extra_info) {
+  UMA_HISTOGRAM_TIMES(
+      internal::kHistogramSessionRestoreForegroundTabFirstContentfulPaint,
+      timing.paint_timing->first_contentful_paint.value());
+}
+
+void SessionRestoreForegroundTabPageLoadMetricsObserver::
+    OnFirstMeaningfulPaintInMainFrameDocument(
+        const page_load_metrics::mojom::PageLoadTiming& timing,
+        const page_load_metrics::PageLoadExtraInfo& extra_info) {
+  UMA_HISTOGRAM_TIMES(
+      internal::kHistogramSessionRestoreForegroundTabFirstMeaningfulPaint,
+      timing.paint_timing->first_meaningful_paint.value());
+}
+
+bool SessionRestoreForegroundTabPageLoadMetricsObserver::
+    IsDuringSessionRestore() const {
+  resource_coordinator::TabManager* tab_manager =
+      g_browser_process->GetTabManager();
+  if (tab_manager)

[fmeawad, 2017/06/09 21:22:27]

Are we expecting to always have a tab_manager, if so then this should be a
DCHECK instead, if not, then maybe we are initializing this too early.

[ducbui, 2017/06/10 00:40:16]

I think the check is necessary because the tab_manager is null on non-supported
platforms such as Android (see
https://cs.chromium.org/chromium/src/chrome/browser/browser_process.h?type=cs...).

[fmeawad, 2017/06/12 14:56:40]

I see, then maybe exclude this code on non-supported devices using ifdefs? If
this is a common pattern then leave it as is, otherwise use ifdefs

+    return tab_manager->IsDuringSessionRestore();
+
+  return false;
+}