Add WebFont.HadBlankText and WebFont.BlankTextShownTime histograms

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 5e018fb0cd24a26eb62abc8b14b6baaa2043901e..011a576cb9ab13f327dfd13cc4811c6b64c19677 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -24001,6 +24001,14 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="WebFont.BlankTextShownTime" units="milliseconds">
+  <summary>
+    A histogram tracking the time we spent showing blank text because a web font
+    wasn't available by the time we needed it. Measured once per @font-face that
+    ended up showing blank text.
+  </summary>
+</histogram>
+
 <histogram name="WebFont.CacheHit" enum="WebFontCacheHit">
   <summary>
     Recorded upon web fonts load. Counts the number of times web font is loaded
@@ -24051,6 +24059,14 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="WebFont.HadBlankText" enum="BooleanHadBlankText">
+  <summary>
+    This metrics is logged when a page that use web fonts is loaded. The value
+    is whether we had to wait on at least one web font and ended up showing
+    blank text, or not.
+  </summary>
+</histogram>
+
 <histogram name="WebFont.LayoutLatency" units="milliseconds">
   <obsolete>
     Renamed to WebFont.StyleRecalcToDownloadLatency for clarity.
@@ -25005,6 +25021,11 @@ other types of suffix sets.
   <int value="1" label="Force Disabled"/>
 </enum>
 
+<enum name="BooleanHadBlankText" type="int">
+  <int value="0" label="Did not have blank text"/>
+  <int value="1" label="Had blank text"/>
+</enum>
+
 <enum name="BooleanHasCrc" type="int">
   <int value="0" label="No CRC"/>
   <int value="1" label="Has CRC"/>