Plumb experiment flags through page_load_metrics and add a new observer

chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..423c8d8983b0485c4df22505bee115c6af96aa8b
--- /dev/null
+++ b/chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.cc
@@ -0,0 +1,116 @@
+// 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/page_load_metrics/observers/document_write_page_load_metrics_observer.h"
+#include "components/page_load_metrics/browser/page_load_metrics_util.h"
+#include "third_party/WebKit/public/platform/WebLoadingBehaviorFlag.h"
+
+namespace internal {
+const char kHistogramDocWriteFirstContentfulPaint[] =
+    "PageLoad.Clients.DocWrite.Evaluator.NavigationToFirstContentfulPaint";
+const char kHistogramDocWriteParseStartToFirstContentfulPaint[] =
+    "PageLoad.Clients.DocWrite.Evaluator.ParseStartToFirstContentfulPaint";
+const char kHistogramDocWriteParseDuration[] =
+    "PageLoad.Clients.DocWrite.Evaluator.ParseDuration";
+const char kHistogramDocWriteParseBlockedOnScript[] =
+    "PageLoad.Clients.DocWrite.Evaluator.ParseBlockedOnScriptLoad";
+const char kHistogramDocWriteParseBlockedOnScriptParseComplete[] =
+    "PageLoad.Clients.DocWrite.Evaluator.ParseBlockedOnScriptLoad."
+    "ParseComplete";
+const char kHistogramDocWriteParseBlockedOnScriptLoadDocumentWrite[] =
+    "PageLoad.Clients.DocWrite.Evaluator."
+    "ParseBlockedOnScriptLoadFromDocumentWrite";
+const char
+    kHistogramDocWriteParseBlockedOnScriptLoadDocumentWriteParseComplete[] =
+        "PageLoad.Clients.DocWrite.Evaluator."
+        "ParseBlockedOnScriptLoadFromDocumentWrite.ParseComplete";
+
+const char kBackgroundHistogramDocWriteFirstContentfulPaint[] =
+    "PageLoad.Clients.DocWrite.Evaluator.NavigationToFirstContentfulPaint."
+    "Background";
+const char kBackgroundHistogramDocWriteParseDuration[] =
+    "PageLoad.Clients.DocWrite.Evaluator.ParseDuration.Background";
+const char kBackgroundHistogramDocWriteParseBlockedOnScript[] =
+    "PageLoad.Clients.DocWrite.Evaluator.ParseBlockedOnScriptLoad.Background";
+const char kBackgroundHistogramDocWriteParseBlockedOnScriptLoadDocumentWrite[] =
+    "PageLoad.Clients.DocWrite.Evaluator."
+    "ParseBlockedOnScriptLoadFromDocumentWrite.Background";
+
+}  // namespace internal
+
+DocumentWritePageLoadMetricsObserver::DocumentWritePageLoadMetricsObserver() {}
+
+void DocumentWritePageLoadMetricsObserver::OnComplete(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  if (info.time_to_commit.is_zero() || timing.IsEmpty())
+    return;
+  if (info.metadata.behavior_flags &
+      blink::WebLoadingBehaviorFlag::WebLoadingBehaviorDocumentWriteEvaluator) {
+    LogDocumentWriteEvaluatorData(timing, info);
+  }
+}
+
+void DocumentWritePageLoadMetricsObserver::LogDocumentWriteEvaluatorData(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  bool foreground_paint = WasStartedInForegroundEventInForeground(
+      timing.first_contentful_paint, info);
+  if (foreground_paint) {
+    PAGE_LOAD_HISTOGRAM(internal::kHistogramDocWriteFirstContentfulPaint,
+                        timing.first_contentful_paint);
+  } else {
+    PAGE_LOAD_HISTOGRAM(
+        internal::kBackgroundHistogramDocWriteFirstContentfulPaint,
+        timing.first_contentful_paint);
+  }
+
+  // Log parse based metrics.
+  if (!timing.parse_start.is_zero()) {
+    if (foreground_paint) {
+      PAGE_LOAD_HISTOGRAM(
+          internal::kHistogramDocWriteParseStartToFirstContentfulPaint,
+          timing.first_contentful_paint - timing.parse_start);
+    }
+
+    const bool incomplete_parse_in_foreground =
+        timing.parse_stop.is_zero() && info.started_in_foreground &&
+        info.first_background_time.is_zero();
+    if (incomplete_parse_in_foreground ||
+        WasStartedInForegroundEventInForeground(timing.parse_stop, info)) {
+      PAGE_LOAD_HISTOGRAM(internal::kHistogramDocWriteParseBlockedOnScript,
+                          timing.parse_blocked_on_script_load_duration);
+      PAGE_LOAD_HISTOGRAM(
+          internal::kHistogramDocWriteParseBlockedOnScriptLoadDocumentWrite,
+          timing.parse_blocked_on_script_load_from_document_write_duration);
+    } else {
+      PAGE_LOAD_HISTOGRAM(
+          internal::kBackgroundHistogramDocWriteParseBlockedOnScript,
+          timing.parse_blocked_on_script_load_duration);
+      PAGE_LOAD_HISTOGRAM(
+          internal::
+              kBackgroundHistogramDocWriteParseBlockedOnScriptLoadDocumentWrite,
+          timing.parse_blocked_on_script_load_from_document_write_duration);
+    }
+
+    // These metrics require a full parse.
+    if (!timing.parse_stop.is_zero()) {
+      base::TimeDelta parse_duration = timing.parse_stop - timing.parse_start;
+      if (WasStartedInForegroundEventInForeground(timing.parse_stop, info)) {
+        PAGE_LOAD_HISTOGRAM(internal::kHistogramDocWriteParseDuration,
+                            parse_duration);
+        PAGE_LOAD_HISTOGRAM(
+            internal::kHistogramDocWriteParseBlockedOnScriptParseComplete,
+            timing.parse_blocked_on_script_load_duration);
+        PAGE_LOAD_HISTOGRAM(
+            internal::
+                kHistogramDocWriteParseBlockedOnScriptLoadDocumentWriteParseComplete,
+            timing.parse_blocked_on_script_load_from_document_write_duration);
+      } else {
+        PAGE_LOAD_HISTOGRAM(internal::kBackgroundHistogramDocWriteParseDuration,
+                            parse_duration);
+      }
+    }
+  }
+}