[Downloads] Some UMA for downloads resumption.

content/browser/download/download_stats.h

Index: content/browser/download/download_stats.h
diff --git a/content/browser/download/download_stats.h b/content/browser/download/download_stats.h
index 287b34d850c34dd77fbdd9b967efee2bc5b3e772..be2ae4b56798527df1a766f2f49aeeffb27fe611 100644
--- a/content/browser/download/download_stats.h
+++ b/content/browser/download/download_stats.h
@@ -68,6 +68,14 @@ enum DownloadCountTypes {
   // successful invocation of ScanAndSaveDownloadedFile().
   FILE_MISSING_AFTER_SUCCESSFUL_SCAN_COUNT,
 
+  // Count of downloads that supplies a strong ETag and has a 'Accept-Ranges:
+  // bytes' header. These downloads are candidates for partial resumption.
+  STRONG_ETAG_AND_ACCEPTS_RANGES,
+
+  // Count of downloads that didn't have a valid WebContents at the time it was
+  // interrupted.
+  INTERRUPTED_WITHOUT_WEBCONTENTS,
+
   DOWNLOAD_COUNT_TYPES_LAST_ENTRY
 };
 
@@ -85,6 +93,13 @@ enum DownloadSource {
   // (e.g. by Alt-click) through the IPC ViewHostMsg_DownloadUrl.
   INITIATED_BY_RENDERER,
 
+  // Fomerly INITIATED_BY_PEPPER_SAVE.
+  DOWNLOAD_SOURCE_UNUSED_3,
+
+  // A request that was initiated as a result of resuming an interrupted
+  // download.
+  INITIATED_BY_RESUMPTION,
+
   DOWNLOAD_SOURCE_LAST_ENTRY
 };
 
@@ -141,8 +156,11 @@ void RecordBandwidth(double actual_bandwidth, double potential_bandwidth);
 // download completed.
 void RecordOpen(const base::Time& end, bool first);
 
-// Record whether or not the server accepts ranges, and the download size.
-void RecordAcceptsRanges(const std::string& accepts_ranges, int64 download_len);
+// Record whether or not the server accepts ranges, and the download size. Also
+// counts if a strong ETag is supplied. The combination of range request support
+// and ETag indicates downloads that are candidates for partial resumption.
+void RecordAcceptsRanges(const std::string& accepts_ranges, int64 download_len,
+                         const std::string& etag);
 
 // Record the number of downloads removed by ClearAll.
 void RecordClearAllSize(int size);