Add UMA for studying download cancellation reasons

chrome/browser/android/download/download_manager_service.cc

Index: chrome/browser/android/download/download_manager_service.cc
diff --git a/chrome/browser/android/download/download_manager_service.cc b/chrome/browser/android/download/download_manager_service.cc
index ab9b1fd7c28f3494ebedce06e5697fdd533d14fe..4a2a68770cfdac4a8c146fcd3453200521136044 100644
--- a/chrome/browser/android/download/download_manager_service.cc
+++ b/chrome/browser/android/download/download_manager_service.cc
@@ -75,8 +75,14 @@ void DownloadManagerService::CancelDownload(
     JNIEnv* env,
     jobject obj,
     const JavaParamRef<jstring>& jdownload_guid,
-    bool is_off_the_record) {
+    bool is_off_the_record,
+    bool is_notification_dismissed) {
   std::string download_guid = ConvertJavaStringToUTF8(env, jdownload_guid);
+
+  content::DownloadControllerAndroid::RecordDownloadCancelReason(
+      is_notification_dismissed ?
+          content::DownloadControllerAndroid::kNotificationDismissed :
+          content::DownloadControllerAndroid::kActionButton);
   // Incognito download can only be cancelled in the same browser session, no
   // need to wait for download history.
   if (is_off_the_record) {