Ensure the 1993 NTP logs to UMA Most Visited tiles that use the fallback thumbnail instead of the preferred one.

TBR=sky@chromium.org

Review URL: https://chromiumcodereview.appspot.com/23874005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221463 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 63 insertions, 7 deletions

diff --git a/chrome/browser/resources/local_ntp/most_visited_thumbnail.js b/chrome/browser/resources/local_ntp/most_visited_thumbnail.js
index 8952d70..dd3f4fd 100644
--- a/chrome/browser/resources/local_ntp/most_visited_thumbnail.js
+++ b/chrome/browser/resources/local_ntp/most_visited_thumbnail.js
@@ -51,9 +51,11 @@ window.addEventListener('DOMContentLoaded', function() {
         // The first thumbnail's onerror function will swap the visibility of
         // the two thumbnails.
         image.onerror = function() {
+          logEvent(NTP_LOGGING_EVENT_TYPE.NTP_FALLBACK_THUMBNAIL_USED);
           image.style.visibility = 'hidden';
           image2.style.visibility = 'visible';
         };
+        logEvent(NTP_LOGGING_EVENT_TYPE.NTP_FALLBACK_THUMBNAIL_REQUESTED);
       } else {
         image.onerror = showDomainElement;
       }
diff --git a/chrome/browser/resources/local_ntp/most_visited_util.js b/chrome/browser/resources/local_ntp/most_visited_util.js
index 446b7ca..3e058bc 100644
--- a/chrome/browser/resources/local_ntp/most_visited_util.js
+++ b/chrome/browser/resources/local_ntp/most_visited_util.js
@@ -19,8 +19,15 @@ var NTP_LOGGING_EVENT_TYPE = {
   NTP_MOUSEOVER: 0,
   // The page attempted to load a thumbnail image.
   NTP_THUMBNAIL_ATTEMPT: 1,
-  // There was an error in loading a thumbnail image.
-  NTP_THUMBNAIL_ERROR: 2
+  // There was an error in loading both the thumbnail image and the fallback
+  // (if it was provided), resulting in a grey tile.
+  NTP_THUMBNAIL_ERROR: 2,
+  // The page attempted to load a thumbnail URL while a fallback thumbnail was
+  // provided.
+  NTP_FALLBACK_THUMBNAIL_REQUESTED: 3,
+  // The primary thumbnail image failed to load and caused us to use the
+  // secondary thumbnail as a fallback.
+  NTP_FALLBACK_THUMBNAIL_USED: 4
 };
 
 /**
diff --git a/chrome/browser/ui/webui/ntp/ntp_user_data_logger.cc b/chrome/browser/ui/webui/ntp/ntp_user_data_logger.cc
index 95d86ed..f3383de 100644
--- a/chrome/browser/ui/webui/ntp/ntp_user_data_logger.cc
+++ b/chrome/browser/ui/webui/ntp/ntp_user_data_logger.cc
@@ -16,12 +16,23 @@ NTPUserDataLogger::~NTPUserDataLogger() {}
 void NTPUserDataLogger::EmitThumbnailErrorRate() {
   DCHECK_LE(number_of_thumbnail_errors_, number_of_thumbnail_attempts_);
   if (number_of_thumbnail_attempts_ != 0) {
-    UMA_HISTOGRAM_PERCENTAGE("NewTabPage.ThumbnailErrorRate",
-                             GetPercentError(number_of_thumbnail_errors_,
-                                             number_of_thumbnail_attempts_));
+    UMA_HISTOGRAM_PERCENTAGE(
+      "NewTabPage.ThumbnailErrorRate",
+      GetPercentError(number_of_thumbnail_errors_,
+                      number_of_thumbnail_attempts_));
+  }
+  DCHECK_LE(number_of_fallback_thumbnails_used_,
+            number_of_fallback_thumbnails_requested_);
+  if (number_of_fallback_thumbnails_requested_ != 0) {
+    UMA_HISTOGRAM_PERCENTAGE(
+        "NewTabPage.ThumbnailFallbackRate",
+        GetPercentError(number_of_fallback_thumbnails_used_,
+                        number_of_fallback_thumbnails_requested_));
   }
   number_of_thumbnail_attempts_ = 0;
   number_of_thumbnail_errors_ = 0;
+  number_of_fallback_thumbnails_requested_ = 0;
+  number_of_fallback_thumbnails_used_ = 0;
 }
 
 void NTPUserDataLogger::EmitMouseoverCount() {
@@ -40,6 +51,12 @@ void NTPUserDataLogger::LogEvent(NTPLoggingEventType event) {
     case NTP_THUMBNAIL_ERROR:
       number_of_thumbnail_errors_++;
       break;
+    case NTP_FALLBACK_THUMBNAIL_REQUESTED:
+      number_of_fallback_thumbnails_requested_++;
+      break;
+    case NTP_FALLBACK_THUMBNAIL_USED:
+      number_of_fallback_thumbnails_used_++;
+      break;
     default:
       NOTREACHED();
   }
@@ -64,7 +81,9 @@ NTPUserDataLogger::NTPUserDataLogger(content::WebContents* contents)
     : content::WebContentsObserver(contents),
       number_of_mouseovers_(0),
       number_of_thumbnail_attempts_(0),
-      number_of_thumbnail_errors_(0) {
+      number_of_thumbnail_errors_(0),
+      number_of_fallback_thumbnails_requested_(0),
+      number_of_fallback_thumbnails_used_(0) {
 }
 
 size_t NTPUserDataLogger::GetPercentError(size_t errors, size_t events) const {
diff --git a/chrome/browser/ui/webui/ntp/ntp_user_data_logger.h b/chrome/browser/ui/webui/ntp/ntp_user_data_logger.h
index 41cd59d..dc1df81 100644
--- a/chrome/browser/ui/webui/ntp/ntp_user_data_logger.h
+++ b/chrome/browser/ui/webui/ntp/ntp_user_data_logger.h
@@ -64,6 +64,14 @@ class NTPUserDataLogger
   // of a thumbnail image.
   size_t number_of_thumbnail_errors_;
 
+  // Total number of attempts made to load thumbnail images while providing a
+  // fallback thumbnail for this NTP session.
+  size_t number_of_fallback_thumbnails_requested_;
+
+  // Total number of errors that occurred while trying to load the primary
+  // thumbnail image and that caused a fallback to the secondary thumbnail.
+  size_t number_of_fallback_thumbnails_used_;
+
   // The URL of this New Tab Page - varies based on NTP version.
   GURL ntp_url_;
 
diff --git a/chrome/common/ntp_logging_events.h b/chrome/common/ntp_logging_events.h
index 3a95a59..8bc8738 100644
--- a/chrome/common/ntp_logging_events.h
+++ b/chrome/common/ntp_logging_events.h
@@ -13,9 +13,18 @@ enum NTPLoggingEventType {
   // The page attempted to load a thumbnail image.
   NTP_THUMBNAIL_ATTEMPT = 1,
 
-  // There was an error in loading a thumbnail image.
+  // There was an error in loading both the thumbnail image and the fallback
+  // (if it was provided), resulting in a grey tile.
   NTP_THUMBNAIL_ERROR = 2,
 
+  // The page attempted to load a thumbnail URL while a fallback thumbnail was
+  // provided.
+  NTP_FALLBACK_THUMBNAIL_REQUESTED = 3,
+
+  // The primary thumbnail image failed to load and caused us to use the
+  // secondary thumbnail as a fallback.
+  NTP_FALLBACK_THUMBNAIL_USED = 4,
+
   NTP_NUM_EVENT_TYPES
 };
 
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 07d31f9..92a3e21 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -10122,6 +10122,17 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="NewTabPage.ThumbnailFallbackRate" units="%">
+  <summary>
+    The percentage of times most visited tiles use the fallback thumbnail. Only
+    requests that actually specify a fallback thumbnail are considered here. We
+    measure the rate instead of the number of errors because multiple attempts
+    are made to load thumbnails at different times during the NTP's lifetime.
+    Each NTP session's error rate is logged after the user navigates to a new
+    URL from that NTP.
+  </summary>
+</histogram>
+
 <histogram name="NewTabPage.VisibleScreenshots">
   <summary>
     The number of screenshots that were cached for the visible suggestions on