Log text/calendar MIME type downloads.

This adds a new value to Download.IOSDownloadMimeType histogram.
text/calendar could be a common email attachment and this histogram will
allow to understand if Chrome should support "Add To Calendar" UI for
these downloads.

Bug: 666211
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: Iafd9d30b1b3c565b38fd5c324bb8767ac1bc61b2
Reviewed-on: https://chromium-review.googlesource.com/1247064Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594729}

ios/chrome/browser/download/browser_download_service.h

@@ -36,7 +36,9 @@ enum class DownloadMimeTypeResult {
   AndroidPackageArchive = 5,
   // text/vcard MIME type.
   VirtualContactFile = 6,
-  kMaxValue = VirtualContactFile,
+  // text/calendar MIME type.
+  iCalendar = 7,
+  kMaxValue = iCalendar,
 };
 
 // Keyed Service which acts as web::DownloadController delegate and routes

ios/chrome/browser/download/browser_download_service.mm

@@ -36,6 +36,9 @@ DownloadMimeTypeResult GetUmaResult(const std::string& mime_type) {
   if (mime_type == "text/vcard")
     return DownloadMimeTypeResult::VirtualContactFile;
 
+  if (mime_type == "text/calendar")
+    return DownloadMimeTypeResult::iCalendar;
+
   return DownloadMimeTypeResult::Other;
 }
 }  // namespace

tools/metrics/histograms/enums.xml

@@ -12093,6 +12093,7 @@ Called by update_net_error_codes.py.-->
     application/vnd.android.package-archive MIME type.
   </int>
   <int value="6" label="Virtual Contact File">text/vcard MIME type.</int>
+  <int value="7" label="iCalendar">text/calendar MIME type.</int>
 </enum>
 
 <enum name="DownloadNotificationForegroundLifecycle">