[CPM Update] Split LoadingStarted event out of navigation histogram.

This way the events in navigation histogram are mutually exclusive.
Also updated histograms.xml and enum.xml which I forgot to update earlier.

Bug: 786551
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I19152cc808e41d6d7a019875145b895a0e48ba0e
Reviewed-on: https://chromium-review.googlesource.com/786670
Commit-Queue: Danyao Wang <danyao@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519815}

ios/chrome/browser/metrics/ios_chrome_stability_metrics_provider.h

@@ -22,8 +22,10 @@ class IOSChromeStabilityMetricsProvider : public metrics::MetricsProvider,
                                           public web::GlobalWebStateObserver {
  public:
   // Buckets for the histogram that counts events relevant for counting page
-  // loads. The *_NAVIGATION events are mutually exclusive.
-  enum class StabilityMetricEventType {
+  // loads. These events are mutually exclusive.
+  // These values are persisted to logs. Entries should not be renumbered and
+  // numeric values should never be reused.
+  enum class PageLoadCountNavigationType {
     // A chrome:// URL navigation. This is not counted for page load.
     CHROME_URL_NAVIGATION = 0,
     // A same-document web (i.e. not chrome:// URL) navigation. This is not
@@ -32,10 +34,10 @@ class IOSChromeStabilityMetricsProvider : public metrics::MetricsProvider,
     // A navigation that is not SAME_DOCUMENT_WEB or CHROME_URL. It is counted
     // as a page load.
     PAGE_LOAD_NAVIGATION = 2,
-    // A loading start event. This is the legacy page load count.
-    // TODO(crbug.com/786547): Deprecate this counter after page load count cuts
-    // over to be based on DidStartNavigation.
-    LOADING_STARTED = 3,
+
+    // OBSOLETE VALUES. DO NOT REUSE.
+    OBSOLETE_LOADING_STARTED = 3,
+
     COUNT
   };
 
@@ -59,7 +61,8 @@ class IOSChromeStabilityMetricsProvider : public metrics::MetricsProvider,
   // Records a renderer process crash.
   void LogRendererCrash();
 
-  static const char kPageLoadCountMigrationEventKey[];
+  static const char kPageLoadCountLoadingStartedMetric[];
+  static const char kPageLoadCountMetric[];
 
  private:
   metrics::StabilityMetricsHelper helper_;

ios/chrome/browser/metrics/ios_chrome_stability_metrics_provider.mm

@@ -13,9 +13,13 @@
 #error "This file requires ARC support."
 #endif
 
+// Name of the UMA enum histogram that counts DidStartNavigation events by type.
+const char IOSChromeStabilityMetricsProvider::kPageLoadCountMetric[] =
+    "IOS.PageLoadCount.Counts";
+// Name of the UMA enum history that counts DidStartLoading events.
 const char
-    IOSChromeStabilityMetricsProvider::kPageLoadCountMigrationEventKey[] =
-        "IOS.PageLoadCountMigration.Counts";
+    IOSChromeStabilityMetricsProvider::kPageLoadCountLoadingStartedMetric[] =
+        "IOS.PageLoadCount.LoadingStarted";
 
 IOSChromeStabilityMetricsProvider::IOSChromeStabilityMetricsProvider(
     PrefService* local_state)
@@ -58,9 +62,7 @@ void IOSChromeStabilityMetricsProvider::WebStateDidStartLoading(
   if (!recording_enabled_)
     return;
 
-  UMA_HISTOGRAM_ENUMERATION(kPageLoadCountMigrationEventKey,
-                            StabilityMetricEventType::LOADING_STARTED,
-                            StabilityMetricEventType::COUNT);
+  UMA_HISTOGRAM_BOOLEAN(kPageLoadCountLoadingStartedMetric, true);
   helper_.LogLoadStarted();
 }
 
@@ -70,17 +72,17 @@ void IOSChromeStabilityMetricsProvider::WebStateDidStartNavigation(
   if (!recording_enabled_)
     return;
 
-  StabilityMetricEventType type =
-      StabilityMetricEventType::PAGE_LOAD_NAVIGATION;
+  PageLoadCountNavigationType type =
+      PageLoadCountNavigationType::PAGE_LOAD_NAVIGATION;
   if (navigation_context->GetUrl().SchemeIs(kChromeUIScheme)) {
-    type = StabilityMetricEventType::CHROME_URL_NAVIGATION;
+    type = PageLoadCountNavigationType::CHROME_URL_NAVIGATION;
   } else if (navigation_context->IsSameDocument()) {
-    type = StabilityMetricEventType::SAME_DOCUMENT_WEB_NAVIGATION;
+    type = PageLoadCountNavigationType::SAME_DOCUMENT_WEB_NAVIGATION;
   } else {
     // TODO(crbug.com/786547): Move helper_.LogLoadStarted() here.
   }
-  UMA_HISTOGRAM_ENUMERATION(kPageLoadCountMigrationEventKey, type,
-                            StabilityMetricEventType::COUNT);
+  UMA_HISTOGRAM_ENUMERATION(kPageLoadCountMetric, type,
+                            PageLoadCountNavigationType::COUNT);
 }
 
 void IOSChromeStabilityMetricsProvider::RenderProcessGone(

ios/chrome/browser/metrics/ios_chrome_stability_metrics_provider_unittest.mm

@@ -45,8 +45,8 @@ TEST_F(IOSChromeStabilityMetricsProviderTest,
 
   EXPECT_EQ(0, system_profile.stability().page_load_count());
   EXPECT_TRUE(histogram_tester_
-                  .GetTotalCountsForPrefix(IOSChromeStabilityMetricsProvider::
-                                               kPageLoadCountMigrationEventKey)
+                  .GetTotalCountsForPrefix(
+                      IOSChromeStabilityMetricsProvider::kPageLoadCountMetric)
                   .empty());
 
   // A load should increment metrics if recording is enabled.
@@ -57,12 +57,8 @@ TEST_F(IOSChromeStabilityMetricsProviderTest,
   provider.ProvideStabilityMetrics(&system_profile);
 
   EXPECT_EQ(1, system_profile.stability().page_load_count());
-  histogram_tester_.ExpectUniqueSample(
-      IOSChromeStabilityMetricsProvider::kPageLoadCountMigrationEventKey,
-      static_cast<base::HistogramBase::Sample>(
-          IOSChromeStabilityMetricsProvider::StabilityMetricEventType::
-              LOADING_STARTED),
-      1);
+  histogram_tester_.ExpectTotalCount(
+      IOSChromeStabilityMetricsProvider::kPageLoadCountLoadingStartedMetric, 1);
 }
 
 TEST_F(IOSChromeStabilityMetricsProviderTest,
@@ -75,9 +71,9 @@ TEST_F(IOSChromeStabilityMetricsProviderTest,
   provider.WebStateDidStartNavigation(kNullWebState, &context);
 
   histogram_tester_.ExpectUniqueSample(
-      IOSChromeStabilityMetricsProvider::kPageLoadCountMigrationEventKey,
+      IOSChromeStabilityMetricsProvider::kPageLoadCountMetric,
       static_cast<base::HistogramBase::Sample>(
-          IOSChromeStabilityMetricsProvider::StabilityMetricEventType::
+          IOSChromeStabilityMetricsProvider::PageLoadCountNavigationType::
               SAME_DOCUMENT_WEB_NAVIGATION),
       1);
 
@@ -97,9 +93,9 @@ TEST_F(IOSChromeStabilityMetricsProviderTest,
   provider.WebStateDidStartNavigation(kNullWebState, &context);
 
   histogram_tester_.ExpectUniqueSample(
-      IOSChromeStabilityMetricsProvider::kPageLoadCountMigrationEventKey,
+      IOSChromeStabilityMetricsProvider::kPageLoadCountMetric,
       static_cast<base::HistogramBase::Sample>(
-          IOSChromeStabilityMetricsProvider::StabilityMetricEventType::
+          IOSChromeStabilityMetricsProvider::PageLoadCountNavigationType::
               CHROME_URL_NAVIGATION),
       1);
 
@@ -119,9 +115,9 @@ TEST_F(IOSChromeStabilityMetricsProviderTest,
   provider.WebStateDidStartNavigation(kNullWebState, &context);
 
   histogram_tester_.ExpectUniqueSample(
-      IOSChromeStabilityMetricsProvider::kPageLoadCountMigrationEventKey,
+      IOSChromeStabilityMetricsProvider::kPageLoadCountMetric,
       static_cast<base::HistogramBase::Sample>(
-          IOSChromeStabilityMetricsProvider::StabilityMetricEventType::
+          IOSChromeStabilityMetricsProvider::PageLoadCountNavigationType::
               CHROME_URL_NAVIGATION),
       1);
 
@@ -137,9 +133,9 @@ TEST_F(IOSChromeStabilityMetricsProviderTest, WebNavigationShouldLogPageLoad) {
   provider.WebStateDidStartNavigation(kNullWebState, &context);
 
   histogram_tester_.ExpectUniqueSample(
-      IOSChromeStabilityMetricsProvider::kPageLoadCountMigrationEventKey,
+      IOSChromeStabilityMetricsProvider::kPageLoadCountMetric,
       static_cast<base::HistogramBase::Sample>(
-          IOSChromeStabilityMetricsProvider::StabilityMetricEventType::
+          IOSChromeStabilityMetricsProvider::PageLoadCountNavigationType::
               PAGE_LOAD_NAVIGATION),
       1);
 

tools/metrics/histograms/enums.xml

@@ -22489,6 +22489,13 @@ Called by update_gpu_driver_bug_workaround_entries.py.-->
   <int value="1" label="Remote suggestions"/>
 </enum>
 
+<enum name="IOSPageLoadCountNavigationType">
+  <int value="0" label="Chrome URL Navigation"/>
+  <int value="1" label="Same Document Web Navigation"/>
+  <int value="2" label="Page Load Navigation"/>
+  <int value="3" label="Obsolete - Loading Started"/>
+</enum>
+
 <enum name="IOSRepeatedExternalAppPromptResponse">
   <int value="0" label="Blocked">
     User selected to block the application for the current session.

tools/metrics/histograms/histograms.xml

@@ -30446,6 +30446,32 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="IOS.PageLoadCount.Counts"
+    enum="IOSPageLoadCountNavigationType">
+  <owner>danyao@chromium.org</owner>
+  <summary>The number of navigation started events by navigation type.</summary>
+</histogram>
+
+<histogram name="IOS.PageLoadCount.LoadingStarted">
+  <owner>danyao@chromium.org</owner>
+  <summary>
+    The &quot;true&quot; value of this boolean histogram counts the number of
+    page loading started events. The &quot;false&quot; value will never be seen.
+  </summary>
+</histogram>
+
+<histogram name="IOS.PageLoadCountMigration.Counts"
+    enum="IOSPageLoadCountNavigationType">
+  <obsolete>
+    Deprecated 2017-11.
+  </obsolete>
+  <owner>danyao@chromium.org</owner>
+  <summary>
+    Counts different types of navigation and loading events that are relevant to
+    counting page loads.
+  </summary>
+</histogram>
+
 <histogram name="IOS.PageLoadTiming.OmnibarToPageLoaded" units="ms">
   <owner>danyao@chromium.org</owner>
   <summary>