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

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 443b3af0ba1586ee176759131684aa17ba32c1aa..a910f60f9fe0bc7b2d3779e0a300c27717e33451 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -8879,9 +8879,8 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 <histogram name="Extensions.FeatureProviderStaticInitTime" units="milliseconds">
   <owner>rkaplow@chromium.org</owner>
   <summary>
-    The amount of time that elapsed during
-    extensions::FeatureProvider::Static. Only measured while in the browser
-    process.
+    The amount of time that elapsed during extensions::FeatureProvider::Static.
+    Only measured while in the browser process.
   </summary>
 </histogram>
 
@@ -19591,8 +19590,8 @@ Therefore, the affected-histogram name has to have at least one dot in it.
     enum="QuicSessionLocations">
   <owner>rch@chromium.org</owner>
   <summary>
-    The location in quic_client_session.cc where a session is unexpectedly
-    not going away.
+    The location in quic_client_session.cc where a session is unexpectedly not
+    going away.
   </summary>
 </histogram>
 
@@ -23056,6 +23055,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="NewTabPage.LoadTime">
+  <owner>fserb@chromium.org</owner>
+  <summary>
+    Histogram of the time, in milliseconds, it took for the NTP to load all its
+    tiles since navigation start.
+  </summary>
+</histogram>
+
 <histogram name="NewTabPage.MobilePromo" enum="NewTabPageMobilePromo">
   <obsolete>
     Deprecated on M33 with the change to native NTP.
@@ -23122,9 +23129,9 @@ Therefore, the affected-histogram name has to have at least one dot in it.
     The number of tiles for which we relied on external tiles as a fallback
     because a local screenshot was not available to be used as a thumbnail.
     External tiles are those for which the visuals are handled by the page
-    itself, not by the iframe. Recorded before changing focus away from the NTP,
-    be it bynavigating to a URL, switching tabs, changing the active window or
-    closing the tab/shutting down Chrome.
+    itself, not by the iframe. Recorded before reloading the suggestions,
+    navigating to a URL, switching tabs, changing the active window, or closing
+    the tab/shutting down Chrome.
   </summary>
 </histogram>
 
@@ -23133,9 +23140,9 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>
     The number of external tiles that are displayed on the NTP. External tiles
     are those for which the visuals are handled by the page itself, not by the
-    iframe. Recorded before changing focus away from the NTP, be it by
-    navigating to a URL, switching tabs, changing the active window or closing
-    the tab/shutting down Chrome.
+    iframe. Recorded before reloading the suggestions, navigating to a URL,
+    switching tabs, changing the active window or closing the tab/shutting down
+    Chrome.
   </summary>
 </histogram>
 
@@ -23144,9 +23151,9 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>
     The number of tiles for which we displayed a gray tile with the domain name
     as a fallback because a local screenshot was not available to be used as a
-    thumbnail. Recorded before changing focus away from the NTP, be it by
-    navigating to a URL, switching tabs, changing the active window or closing
-    the tab/shutting down Chrome.
+    thumbnail. Recorded before reloading the suggestions, navigating to a URL,
+    switching tabs, changing the active window or closing the tab/shutting down
+    Chrome.
   </summary>
 </histogram>
 
@@ -23155,8 +23162,8 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>
     The number of tiles for which no thumbnail was specified, but a domain was
     so we displayed a gray tile with the domain name in it. Recorded before
-    changing focus away from the NTP, be it by navigating to a URL, switching
-    tabs, changing the active window or closing the tab/shutting down Chrome.
+    reloading the suggestions, navigating to a URL, switching tabs, changing the
+    active window or closing the tab/shutting down Chrome.
   </summary>
 </histogram>
 
@@ -23177,9 +23184,9 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
     The number of tiles for which we attempted to use a local screenshot as a
-    thumbnail. Recorded before changing focus away from the NTP, be it by
-    navigating to a URL, switching tabs, changing the active window or closing
-    the tab/shutting down Chrome.
+    thumbnail. Recorded before reloading the suggestions, navigating to a URL,
+    switching tabs, changing the active window or closing the tab/shutting down
+    Chrome.
   </summary>
 </histogram>
 
@@ -23188,9 +23195,8 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>
     The number of thumbnails for which a local screenshot was not available so
     we were not able to display them on the Most Visited section of the NTP.
-    Recorded before changing focus away from the NTP, be it by navigating to a
-    URL, switching tabs, changing the active window or closing the tab/shutting
-    down Chrome.
+    Recorded before reloading the suggestions, navigating to a URL, switching
+    tabs, changing the active window or closing the tab/shutting down Chrome.
   </summary>
 </histogram>
 
@@ -23198,9 +23204,9 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <owner>beaudoin@chromium.org</owner>
   <summary>
     The number of tiles for which we attempted to use a local screenshot as a
-    thumbnail. Recorded before changing focus away from the NTP, be it by
-    navigating to a URL, switching tabs, changing the active window or closing
-    the tab/shutting down Chrome.
+    thumbnail. Recorded before reloading the suggestions, navigating to a URL,
+    switching tabs, changing the active window or closing the tab/shutting down
+    Chrome.
   </summary>
 </histogram>
 
@@ -23208,9 +23214,9 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <owner>beaudoin@chromium.org</owner>
   <summary>
     The number of tiles that are displayed on the NTP, no matter if they are
-    thumbnails, gray tiles, or external tiles. Recorded before changing focus
-    away from the NTP, be it by navigating to a URL, switching tabs, changing
-    the active window or closing the tab/shutting down Chrome.
+    thumbnails, gray tiles, or external tiles. Recorded before reloading the
+    suggestions, navigating to a URL, switching tabs, changing the active window
+    or closing the tab/shutting down Chrome.
   </summary>
 </histogram>