Add startup metrics that measure the performance of the first web contents.

I added two metrics: "Startup.FirstWebContents.MainFrameLoad" and
"Startup.FirstWebContents.NonEmptyPaint".

BUG=436152

Review URL: https://codereview.chromium.org/760763002

Cr-Commit-Position: refs/heads/master@{#306884}

6 files changed, 277 insertions, 2 deletions

diff --git a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
index 5ca78d2c..3d5e9e7 100644
--- a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
+++ b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
@@ -264,6 +264,14 @@ void ChromeBrowserMainExtraPartsMetrics::PostBrowserStart() {
   UMA_HISTOGRAM_COUNTS_100("Hardware.Display.Count.OnStartup", display_count_);
   gfx::Screen::GetNativeScreen()->AddObserver(this);
   is_screen_observer_ = true;
+
+#if !defined(OS_ANDROID)
+  if (FirstWebContentsProfiler::ShouldCollectMetrics()) {
+    first_web_contents_profiler_ =
+        FirstWebContentsProfiler::CreateProfilerForFirstWebContents(this)
+            .Pass();
+  }
+#endif  // !defined(OS_ANDROID)
 }
 
 void ChromeBrowserMainExtraPartsMetrics::OnDisplayAdded(
@@ -281,6 +289,10 @@ void ChromeBrowserMainExtraPartsMetrics::OnDisplayMetricsChanged(
     uint32_t changed_metrics) {
 }
 
+void ChromeBrowserMainExtraPartsMetrics::ProfilerFinishedCollectingMetrics() {
+  first_web_contents_profiler_.reset();
+}
+
 void ChromeBrowserMainExtraPartsMetrics::EmitDisplaysChangedMetric() {
   int display_count = gfx::Screen::GetNativeScreen()->GetNumDisplays();
   if (display_count != display_count_) {
diff --git a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h
index 91b904d..7d9eceb 100644
--- a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h
+++ b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h
@@ -9,6 +9,7 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/chrome_browser_main_extra_parts.h"
+#include "chrome/browser/metrics/first_web_contents_profiler.h"
 #include "ui/gfx/display_observer.h"
 
 class ChromeBrowserMainParts;
@@ -17,8 +18,10 @@ namespace chrome {
 void AddMetricsExtraParts(ChromeBrowserMainParts* main_parts);
 }
 
-class ChromeBrowserMainExtraPartsMetrics : public ChromeBrowserMainExtraParts,
-                                           public gfx::DisplayObserver {
+class ChromeBrowserMainExtraPartsMetrics
+    : public ChromeBrowserMainExtraParts,
+      public gfx::DisplayObserver,
+      public FirstWebContentsProfiler::Delegate {
  public:
   ChromeBrowserMainExtraPartsMetrics();
   ~ChromeBrowserMainExtraPartsMetrics() override;
@@ -40,6 +43,9 @@ class ChromeBrowserMainExtraPartsMetrics : public ChromeBrowserMainExtraParts,
   virtual void OnDisplayMetricsChanged(const gfx::Display& display,
                                        uint32_t changed_metrics) override;
 
+  // FirstWebContentsProfilerDelegate overrides.
+  void ProfilerFinishedCollectingMetrics() override;
+
   // If the number of displays has changed, emit a UMA metric.
   void EmitDisplaysChangedMetric();
 
@@ -50,6 +56,9 @@ class ChromeBrowserMainExtraPartsMetrics : public ChromeBrowserMainExtraParts,
   // screen.
   bool is_screen_observer_;
 
+  // Measures start up performance of the first active web contents.
+  scoped_ptr<FirstWebContentsProfiler> first_web_contents_profiler_;
+
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainExtraPartsMetrics);
 };
 
diff --git a/chrome/browser/metrics/first_web_contents_profiler.cc b/chrome/browser/metrics/first_web_contents_profiler.cc
new file mode 100644
index 0000000..ea6399c
--- /dev/null
+++ b/chrome/browser/metrics/first_web_contents_profiler.cc
@@ -0,0 +1,130 @@
+// Copyright 2014 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.
+
+#if !defined(OS_ANDROID)
+
+#include "chrome/browser/metrics/first_web_contents_profiler.h"
+
+#include "base/metrics/histogram_macros.h"
+#include "base/process/process_info.h"
+#include "base/time/time.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_iterator.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/common/chrome_version_info.h"
+
+namespace {
+
+const int kHistogramMinTimeMilliseconds = 200;
+const int kHistogramMaxTimeSeconds = 45;
+
+// There is a lot of noise in the dev channel. One possible cause is that the
+// bucket ranges are too wide. The bucket count is chosen such that the size of
+// the bucket is 1% of its minimum. Notice that this also means that
+// subsequent buckets will satisfy Min(bucket N + 1) / Min(bucket N) = 1.01.
+// Then we want X, such that 1.01 ^ X = 45 * 1000 / 200. Some quick math shows
+// that X = 544.
+const int kHistogramBucketCount = 544;
+
+}  // namespace
+
+scoped_ptr<FirstWebContentsProfiler>
+FirstWebContentsProfiler::CreateProfilerForFirstWebContents(
+    Delegate* delegate) {
+  DCHECK(delegate);
+  for (chrome::BrowserIterator iterator; !iterator.done(); iterator.Next()) {
+    Browser* browser = *iterator;
+    content::WebContents* web_contents =
+        browser->tab_strip_model()->GetActiveWebContents();
+    if (web_contents) {
+      return scoped_ptr<FirstWebContentsProfiler>(
+          new FirstWebContentsProfiler(web_contents, delegate));
+    }
+  }
+  return nullptr;
+}
+
+bool FirstWebContentsProfiler::ShouldCollectMetrics() {
+  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
+  return channel == chrome::VersionInfo::CHANNEL_CANARY ||
+         channel == chrome::VersionInfo::CHANNEL_DEV;
+}
+
+FirstWebContentsProfiler::FirstWebContentsProfiler(
+    content::WebContents* web_contents,
+    Delegate* delegate)
+    : content::WebContentsObserver(web_contents),
+      collected_paint_metric_(false),
+      collected_load_metric_(false),
+      delegate_(delegate) {
+  process_creation_time_ = base::CurrentProcessInfo::CreationTime();
+}
+
+void FirstWebContentsProfiler::DidFirstVisuallyNonEmptyPaint() {
+  if (collected_paint_metric_)
+    return;
+
+  collected_paint_metric_ = true;
+  if (!process_creation_time_.is_null()) {
+    base::TimeDelta elapsed = base::Time::Now() - process_creation_time_;
+
+    // TODO(erikchen): Revisit these metrics once data has been collected to
+    // determine whether using more buckets reduces noise and provides higher
+    // quality information.
+    UMA_HISTOGRAM_CUSTOM_TIMES(
+        "Startup.Experimental.FirstWebContents.NonEmptyPaint."
+        "ManyBuckets",
+        elapsed,
+        base::TimeDelta::FromMilliseconds(kHistogramMinTimeMilliseconds),
+        base::TimeDelta::FromSeconds(kHistogramMaxTimeSeconds),
+        kHistogramBucketCount);
+    UMA_HISTOGRAM_LONG_TIMES_100(
+        "Startup.Experimental.FirstWebContents.NonEmptyPaint.StandardBuckets",
+        elapsed);
+  }
+
+  if (IsFinishedCollectingMetrics())
+    FinishedCollectingMetrics();
+}
+
+void FirstWebContentsProfiler::DocumentOnLoadCompletedInMainFrame() {
+  if (collected_load_metric_)
+    return;
+
+  collected_load_metric_ = true;
+  if (!process_creation_time_.is_null()) {
+    base::TimeDelta elapsed = base::Time::Now() - process_creation_time_;
+
+    // TODO(erikchen): Revisit these metrics once data has been collected to
+    // determine whether using more buckets reduces noise and provides higher
+    // quality information.
+    UMA_HISTOGRAM_CUSTOM_TIMES(
+        "Startup.Experimental.FirstWebContents.MainFrameLoad."
+        "ManyBuckets",
+        elapsed,
+        base::TimeDelta::FromMilliseconds(kHistogramMinTimeMilliseconds),
+        base::TimeDelta::FromSeconds(kHistogramMaxTimeSeconds),
+        kHistogramBucketCount);
+    UMA_HISTOGRAM_LONG_TIMES_100(
+        "Startup.Experimental.FirstWebContents.MainFrameLoad.StandardBuckets",
+        elapsed);
+  }
+
+  if (IsFinishedCollectingMetrics())
+    FinishedCollectingMetrics();
+}
+
+void FirstWebContentsProfiler::WebContentsDestroyed() {
+  FinishedCollectingMetrics();
+}
+
+bool FirstWebContentsProfiler::IsFinishedCollectingMetrics() {
+  return collected_paint_metric_ && collected_load_metric_;
+}
+
+void FirstWebContentsProfiler::FinishedCollectingMetrics() {
+  delegate_->ProfilerFinishedCollectingMetrics();
+}
+
+#endif  // !defined(OS_ANDROID)
diff --git a/chrome/browser/metrics/first_web_contents_profiler.h b/chrome/browser/metrics/first_web_contents_profiler.h
new file mode 100644
index 0000000..a3bbfe5
--- /dev/null
+++ b/chrome/browser/metrics/first_web_contents_profiler.h
@@ -0,0 +1,76 @@
+// Copyright 2014 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_METRICS_FIRST_WEB_CONTENTS_PROFILER_H_
+#define CHROME_BROWSER_METRICS_FIRST_WEB_CONTENTS_PROFILER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "content/public/browser/web_contents_observer.h"
+
+namespace content {
+class WebContents;
+}  // namespace content
+
+// Measures start up performance of the first active web contents.
+// This class is declared on all platforms, but only defined on non-Android
+// platforms. Android code should not call any non-trivial methods on this
+// class.
+class FirstWebContentsProfiler : public content::WebContentsObserver {
+ public:
+  class Delegate {
+   public:
+    // Called by the FirstWebContentsProfiler when it is finished collecting
+    // metrics. The delegate should take this opportunity to destroy the
+    // FirstWebContentsProfiler.
+    virtual void ProfilerFinishedCollectingMetrics() = 0;
+  };
+
+  // Creates a profiler for the active web contents. If there are multiple
+  // browsers, the first one is chosen. If there are no browsers, returns
+  // nullptr.
+  static scoped_ptr<FirstWebContentsProfiler> CreateProfilerForFirstWebContents(
+      Delegate* delegate);
+
+  // These metrics are currently experimental, and are only collected in the
+  // dev and canary channels.
+  static bool ShouldCollectMetrics();
+
+ private:
+  FirstWebContentsProfiler(content::WebContents* web_contents,
+                           Delegate* delegate);
+
+  // content::WebContentsObserver:
+  void DidFirstVisuallyNonEmptyPaint() override;
+  void DocumentOnLoadCompletedInMainFrame() override;
+  void WebContentsDestroyed() override;
+
+  // Whether this instance has finished collecting all of its metrics.
+  bool IsFinishedCollectingMetrics();
+
+  // Informs the delegate that this instance has finished collecting all of its
+  // metrics.
+  void FinishedCollectingMetrics();
+
+  // Whether the "NonEmptyPaint" metric has been collected. If an attempt is
+  // made to collect the metric but the attempt fails, this member is set to
+  // true to prevent this class from sitting around forever attempting to
+  // collect the metric.
+  bool collected_paint_metric_;
+
+  // Whether the "MainFrameLoad" metric has been collected. If an attempt is
+  // made to collect the metric but the attempt fails, this member is set to
+  // true to prevent this class from sitting around forever attempting to
+  // collect the metric.
+  bool collected_load_metric_;
+
+  // The time at which the process was created.
+  base::Time process_creation_time_;
+
+  // |delegate_| owns |this|.
+  Delegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(FirstWebContentsProfiler);
+};
+
+#endif  // CHROME_BROWSER_METRICS_FIRST_WEB_CONTENTS_PROFILER_H_
diff --git a/chrome/chrome_browser.gypi b/chrome/chrome_browser.gypi
index 700517a..90663e9 100644
--- a/chrome/chrome_browser.gypi
+++ b/chrome/chrome_browser.gypi
@@ -1146,6 +1146,8 @@
       'browser/metrics/chrome_stability_metrics_provider.h',
       'browser/metrics/field_trial_synchronizer.cc',
       'browser/metrics/field_trial_synchronizer.h',
+      'browser/metrics/first_web_contents_profiler.cc',
+      'browser/metrics/first_web_contents_profiler.h',
       'browser/metrics/google_update_metrics_provider_win.cc',
       'browser/metrics/google_update_metrics_provider_win.h',
       'browser/metrics/jumplist_metrics_win.cc',
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 46f0443..c4f6eac 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -35497,6 +35497,52 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram
+    name="Startup.Experimental.FirstWebContents.MainFrameLoad.ManyBuckets"
+    units="milliseconds">
+  <owner>erikchen@chromium.org</owner>
+  <summary>
+    An experimental metric only collected on the dev and canary channels.
+    Measure the elapsed time from process launch to the first main frame load of
+    the first web contents. Uses significantly more buckets, with reduced
+    ranges.
+  </summary>
+</histogram>
+
+<histogram
+    name="Startup.Experimental.FirstWebContents.MainFrameLoad.StandardBuckets"
+    units="milliseconds">
+  <owner>erikchen@chromium.org</owner>
+  <summary>
+    An experimental metric only collected on the dev and canary channels.
+    Measure the elapsed time from process launch to the first main frame load of
+    the first web contents. Uses standard bucket ranges.
+  </summary>
+</histogram>
+
+<histogram
+    name="Startup.Experimental.FirstWebContents.NonEmptyPaint.ManyBuckets"
+    units="milliseconds">
+  <owner>erikchen@chromium.org</owner>
+  <summary>
+    An experimental metric only collected on the dev and canary channels.
+    Measure the elapsed time from process launch to the first non-empty paint of
+    the first web contents. Uses significantly more buckets, with reduced
+    ranges.
+  </summary>
+</histogram>
+
+<histogram
+    name="Startup.Experimental.FirstWebContents.NonEmptyPaint.StandardBuckets"
+    units="milliseconds">
+  <owner>erikchen@chromium.org</owner>
+  <summary>
+    An experimental metric only collected on the dev and canary channels.
+    Measure the elapsed time from process launch to the first non-empty paint of
+    the first web contents. Uses standard bucket ranges.
+  </summary>
+</histogram>
+
 <histogram name="Startup.Fling.TimeToDisplayVideo" units="milliseconds">
   <owner>jeremy@chromium.org</owner>
   <summary>