Isolate initiation counts for downloads to their own histograms and improve

chrome/browser/download/download_util.cc

Index: chrome/browser/download/download_util.cc
diff --git a/chrome/browser/download/download_util.cc b/chrome/browser/download/download_util.cc
index a851c852ed9f6549e674a0db04bccd3415780c0c..00e654d90254752c16d42ffbeb52ca3f94400f12 100644
--- a/chrome/browser/download/download_util.cc
+++ b/chrome/browser/download/download_util.cc
@@ -633,4 +633,9 @@ void RecordDownloadCount(ChromeDownloadCountTypes type) {
       "Download.CountsChrome", type, DOWNLOAD_COUNT_TYPES_LAST_ENTRY);
 }
 
+void RecordDownloadSource(ChromeDownloadInitiationSources source) {
+  UMA_HISTOGRAM_ENUMERATION(
+      "Download.SourcesChrome", source, DOWNLOAD_INITIATION_SOURCES_LAST_ENTRY);
+}
+
 }  // namespace download_util