Use If-Range instead of If-Match/If-Unmodified-Since for partial requests.

chrome/browser/download/download_item_model.cc

Index: chrome/browser/download/download_item_model.cc
diff --git a/chrome/browser/download/download_item_model.cc b/chrome/browser/download/download_item_model.cc
index 6ef6de5f1759abdca7941983a4de2da622efc825..e60d4fc3b49be555fddacc5b144c56d869a4379a 100644
--- a/chrome/browser/download/download_item_model.cc
+++ b/chrome/browser/download/download_item_model.cc
@@ -174,7 +174,6 @@ base::string16 InterruptReasonStatusMessage(int reason) {
       NOTREACHED();
       // fallthrough
     case content::DOWNLOAD_INTERRUPT_REASON_SERVER_NO_RANGE:
-    case content::DOWNLOAD_INTERRUPT_REASON_SERVER_PRECONDITION:
     case content::DOWNLOAD_INTERRUPT_REASON_FILE_FAILED:
       string_id = IDS_DOWNLOAD_INTERRUPTED_STATUS;
   }
@@ -255,7 +254,6 @@ base::string16 InterruptReasonMessage(int reason) {
       NOTREACHED();
       // fallthrough
     case content::DOWNLOAD_INTERRUPT_REASON_SERVER_NO_RANGE:
-    case content::DOWNLOAD_INTERRUPT_REASON_SERVER_PRECONDITION:
     case content::DOWNLOAD_INTERRUPT_REASON_FILE_FAILED:
       string_id = IDS_DOWNLOAD_INTERRUPTED_STATUS;
   }