Isolate initiation counts for downloads to their own histograms and improve

chrome/browser/download/download_util.h

Index: chrome/browser/download/download_util.h
diff --git a/chrome/browser/download/download_util.h b/chrome/browser/download/download_util.h
index 6df96e46bce3154890153569f2d26c8d227da0f9..6f4979e7605346dc4050fd8c729198b9e85110da 100644
--- a/chrome/browser/download/download_util.h
+++ b/chrome/browser/download/download_util.h
@@ -173,23 +173,31 @@ void RecordShelfClose(int size, int in_progress, bool autoclose);
 
 // Used for counting UMA stats. Similar to content's
 // download_stats::DownloadCountTypes but from the chrome layer.
-enum ChromeDownloadCountTypes {
+enum ChromeDownloadInitiationSources {
   // The download was initiated by navigating to a URL (e.g. by user click).
-  INITIATED_BY_NAVIGATION_COUNT = 0,
+  INITIATED_BY_NAVIGATION = 0,
 
   // The download was initiated by invoking a context menu within a page.
-  INITIATED_BY_CONTEXT_MENU_COUNT,
+  INITIATED_BY_CONTEXT_MENU,
 
   // The download was initiated by the WebStore installer.
-  INITIATED_BY_WEBSTORE_INSTALLER_COUNT,
+  INITIATED_BY_WEBSTORE_INSTALLER,
 
   // The download was initiated by the ImageBurner (cros).
-  INITIATED_BY_IMAGE_BURNER_COUNT,
+  INITIATED_BY_IMAGE_BURNER,
 
-  DOWNLOAD_COUNT_TYPES_LAST_ENTRY,
+  // A download *would* have been initiated, but it was blocked
+  // by the DownloadThrottlingResourceHandler.
+  // This is included in this histogram even though it's not a
+  // download initiation because the most likely things to compare this
+  // value against are the other INITIATED_BY_* values (specficially
+  // INITIATED_BY_NAVIGATION).
+  BLOCKED_BY_THROTTLING,
+
+  DOWNLOAD_INITIATION_SOURCES_LAST_ENTRY,
 };
 
-void RecordDownloadCount(ChromeDownloadCountTypes type);
+void RecordDownloadSource(ChromeDownloadInitiationSources source);
 
 }  // namespace download_util