Adds a new UMA histogram to measure the NTP load time since navigation

chrome/browser/ui/webui/ntp/ntp_user_data_logger.cc

Index: chrome/browser/ui/webui/ntp/ntp_user_data_logger.cc
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 35f90b67ef4dccbfc9c5e942c4f0e85dad7b7476..6486c77395d2485f8b2ab5616a1d92f4bce9a142 100644
--- a/chrome/browser/ui/webui/ntp/ntp_user_data_logger.cc
+++ b/chrome/browser/ui/webui/ntp/ntp_user_data_logger.cc
@@ -93,38 +93,51 @@ void NTPUserDataLogger::EmitNtpStatistics() {
   UMA_HISTOGRAM_COUNTS("NewTabPage.NumberOfMouseOvers", number_of_mouseovers_);
   number_of_mouseovers_ = 0;
 
+  // We already sent statistics for this page once.
+  if (has_emitted_) {
+    return;
+  }
+
   // Only log the following statistics if at least one tile is recorded. This
   // check is required because the statistics are emitted whenever the user
   // changes tab away from the NTP. However, if the user comes back to that NTP

[Mathieu, 2015/03/16 19:49:45]

amend comment

[fserb, 2015/03/16 20:08:36]

Done.

   // later the statistics are not regenerated (i.e. they are all 0). If we log
   // them again we get a strong bias.
-  if (number_of_tiles_ > 0) {
-    UMA_HISTOGRAM_ENUMERATION(
-        "NewTabPage.SuggestionsType",
-        has_server_side_suggestions_ ? SERVER_SIDE : CLIENT_SIDE,
-        SUGGESTIONS_TYPE_COUNT);
-    has_server_side_suggestions_ = false;
-    UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfTiles", number_of_tiles_);
-    number_of_tiles_ = 0;
-    UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfThumbnailTiles",
-                            number_of_thumbnail_tiles_);
-    number_of_thumbnail_tiles_ = 0;
-    UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfGrayTiles",
-                            number_of_gray_tiles_);
-    number_of_gray_tiles_ = 0;
-    UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfExternalTiles",
-                            number_of_external_tiles_);
-    number_of_external_tiles_ = 0;
-    UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfThumbnailErrors",
-                            number_of_thumbnail_errors_);
-    number_of_thumbnail_errors_ = 0;
-    UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfGrayTileFallbacks",
-                            number_of_gray_tile_fallbacks_);
-    number_of_gray_tile_fallbacks_ = 0;
-    UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfExternalTileFallbacks",
-                            number_of_external_tile_fallbacks_);
-    number_of_external_tile_fallbacks_ = 0;
+  if (!number_of_tiles_) {
+    return;
   }
+
+  UMA_HISTOGRAM_ENUMERATION(
+      "NewTabPage.SuggestionsType",
+      has_server_side_suggestions_ ? SERVER_SIDE : CLIENT_SIDE,
+      SUGGESTIONS_TYPE_COUNT);
+  has_server_side_suggestions_ = false;
+  UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfTiles", number_of_tiles_);
+  number_of_tiles_ = 0;
+  UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfThumbnailTiles",
+                          number_of_thumbnail_tiles_);
+  number_of_thumbnail_tiles_ = 0;
+  UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfGrayTiles",
+                          number_of_gray_tiles_);
+  number_of_gray_tiles_ = 0;
+  UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfExternalTiles",
+                          number_of_external_tiles_);
+  number_of_external_tiles_ = 0;
+  UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfThumbnailErrors",
+                          number_of_thumbnail_errors_);
+  number_of_thumbnail_errors_ = 0;
+  UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfGrayTileFallbacks",
+                          number_of_gray_tile_fallbacks_);
+  number_of_gray_tile_fallbacks_ = 0;
+  UMA_HISTOGRAM_NTP_TILES("NewTabPage.NumberOfExternalTileFallbacks",
+                          number_of_external_tile_fallbacks_);
+  number_of_external_tile_fallbacks_ = 0;
+  UMA_HISTOGRAM_CUSTOM_TIMES("NewTabPage.LoadTime",
+                             base::TimeDelta::FromMilliseconds(load_time_),
+                             base::TimeDelta::FromMilliseconds(1),
+                             base::TimeDelta::FromSeconds(60), 100);
+  load_time_ = 0;
+  has_emitted_ = true;
 }
 
 void NTPUserDataLogger::LogEvent(NTPLoggingEventType event, uint64 time) {
@@ -162,6 +175,9 @@ void NTPUserDataLogger::LogEvent(NTPLoggingEventType event, uint64 time) {
     case NTP_MOUSEOVER:
       number_of_mouseovers_++;
       break;
+    case NTP_TILE_LOADED:
+      load_time_ = std::max(load_time_, time);

[beaudoin, 2015/03/16 19:39:36]

Add a comment here to indicate that the time at which the last tile has loaded
is a good proxy for the total load time of the NTP, therefore we keep the max.

[fserb, 2015/03/16 19:47:38]

Done.

+      break;
     default:
       NOTREACHED();
   }
@@ -236,5 +252,7 @@ NTPUserDataLogger::NTPUserDataLogger(content::WebContents* contents)
       number_of_thumbnail_errors_(0),
       number_of_gray_tile_fallbacks_(0),
       number_of_external_tile_fallbacks_(0),
-      number_of_mouseovers_(0) {
+      number_of_mouseovers_(0),
+      load_time_(0),
+      has_emitted_(false) {
 }