Material PDF: Add metrics to count usage of PDF title and bookmarks

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 e066f2787a9bca3c4c26a30dd47318b5e1ae3c14..0a3f6d4076bbcc843ac9987a3e6bba46e1b27e28 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -30825,6 +30825,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="PDF.HasFeature" enum="Boolean">
+  <owner>tsergeant@chromium.org</owner>
+  <summary>
+    Tracks which features are used by documents opened in the PDF viewer.
+  </summary>
+</histogram>
+
 <histogram name="Pepper.InterfaceUsed" enum="PepperInterface">
   <owner>mackinlay@google.com</owner>
   <owner>teravest@chromium.org</owner>
@@ -78398,6 +78405,12 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="PasswordManager.TotalAccountsHiRes.WithScheme"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="PDFFeatures" separator=".">
+  <suffix name="Title" label="PDF document has a title field."/>
+  <suffix name="Bookmarks" label="PDF document has a table of contents."/>
+  <affected-histogram name="PDF.HasFeature"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="PerformanceMonitor" separator=".">
   <suffix name="BrowserProcess"/>
   <suffix name="GPUProcess"/>