[Page Load Metrics] Add page load metrics for omnibox.

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 d8275c8c16b1b5ca8ac39b86130383ea24d8fa95..7dc3ae800ab42663cb9127542cd14ddfe0647f5d 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -43984,6 +43984,55 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram
+    name="Omnibox.SuggestionUsed.Search.Experimental.ForegroundToFirstMeaningfulPaint.Prerender"
+    units="ms">
+  <summary>
+    Measures the time from the page first appearing in the foreground to its
+    first meaningful paint. Only recorded on navigations that use a prerender
+    that is to a search query suggestion selected from the omnibox.
+  </summary>
+</histogram>
+
+<histogram
+    name="Omnibox.SuggestionUsed.Search.Experimental.NavigationToFirstMeaningfulPaint"
+    units="ms">
+  <summary>
+    Measures the time from navigation start to first meaningful paint. Only
+    recorded for a search query suggestion selected from the omnibox.
+  </summary>
+</histogram>
+
+<histogram
+    name="Omnibox.SuggestionUsed.Search.ForegroundToFirstContentfulPaint.Prerender"
+    units="ms">
+  <summary>
+    Measures the time from the page first appearing in the foreground to its
+    first contentful paint. Only recorded on navigations that use a prerender
+    that is to a search query suggestion selected from the omnibox.
+  </summary>
+</histogram>
+
+<histogram
+    name="Omnibox.SuggestionUsed.Search.NavigationToFirstContentfulPaint"
+    units="ms">
+  <summary>
+    Measures the time from navigation start to first contentful paint. Only
+    recorded for a search query suggestion selected from the omnibox.
+  </summary>
+</histogram>
+
+<histogram
+    name="Omnibox.SuggestionUsed.Search.NavigationToFirstForeground.Prerender"
+    units="ms">
+  <summary>
+    Measures the time from a page being navigated to in prerender to it first
+    showing up in foreground. Only recorded on navigations that used a prerender
+    that was to a search query suggestion selected from the omnibox. This is
+    only recorded on pages that experience a first contentful paint.
+  </summary>
+</histogram>
+
 <histogram name="Omnibox.SuggestionUsed.SearchVsUrl"
     enum="OmniboxSummarizedResultType">
   <owner>mpearson@google.com</owner>
@@ -43993,6 +44042,54 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram
+    name="Omnibox.SuggestionUsed.URL.Experimental.ForegroundToFirstMeaningfulPaint.Prerender"
+    units="ms">
+  <summary>
+    Measures the time from the page first appearing in the foreground to its
+    first meaningful paint. Only recorded on navigations that use a prerender
+    that is to a URL suggestion selected from the omnibox.
+  </summary>
+</histogram>
+
+<histogram
+    name="Omnibox.SuggestionUsed.URL.Experimental.NavigationToFirstMeaningfulPaint"
+    units="ms">
+  <summary>
+    Measures the time from navigation start to first meaningful paint. Only
+    recorded for a URL suggestion selected from the omnibox.
+  </summary>
+</histogram>
+
+<histogram
+    name="Omnibox.SuggestionUsed.URL.ForegroundToFirstContentfulPaint.Prerender"
+    units="ms">
+  <summary>
+    Measures the time from the page first appearing in the foreground to its
+    first contentful paint. Only recorded on navigations that use a prerender
+    that is to a URL suggestion selected from the omnibox.
+  </summary>
+</histogram>
+
+<histogram name="Omnibox.SuggestionUsed.URL.NavigationToFirstContentfulPaint"
+    units="ms">
+  <summary>
+    Measures the time from navigation start to first contentful paint. Only
+    recorded for a URL suggestion selected from the omnibox.
+  </summary>
+</histogram>
+
+<histogram
+    name="Omnibox.SuggestionUsed.URL.NavigationToFirstForeground.Prerender"
+    units="ms">
+  <summary>
+    Measures the time from a page being navigated to in prerender to it first
+    showing up in foreground. Only recorded on navigations that used a prerender
+    that was to a URL suggestion selected from the omnibox. This is only
+    recorded on pages that experience a first contentful paint.
+  </summary>
+</histogram>
+
 <histogram name="Omnibox.SuggestRequest.Failure.GoogleResponseTime" units="ms">
   <owner>mpearson@chromium.org</owner>
   <summary>