Prefer opening PDF downloads in the browser.

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 e43615147e9cccfb3eacba6890afe9f27203695b..e4ad3d931c4ae96c30dc57e8a516b14be5df22b1 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -3060,6 +3060,14 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Download.OpenMethod" enum="DownloadOpenMethod">
+  <summary>
+    Invocation count for methods of opening a download. For some file types,
+    Chrome defaults to opening the file in the browser instead of invoking the
+    system handler. The user has the option of overriding this behavior.
+  </summary>
+</histogram>
+
 <histogram name="Download.OpensOutstanding">
   <summary>The number of unopened downloads, when one is opened.</summary>
 </histogram>
@@ -21409,6 +21417,12 @@ other types of suffix sets.
   <int value="8" label="POTENTIALLY_UNWANTED"/>
 </enum>
 
+<enum name="DownloadOpenMethod" type="int">
+  <int value="0" label="Opened with plaform handler by default"/>
+  <int value="1" label="Opened in browser by default"/>
+  <int value="2" label="Opened with plaform handler by user choice"/>
+</enum>
+
 <enum name="DownloadSavePackageEvent" type="int">
   <int value="0" label="Started"/>
   <int value="1" label="Cancelled"/>