Add new danger type for uncommon or unknown downloads.

chrome/browser/resources/downloads.js

Index: chrome/browser/resources/downloads.js
diff --git a/chrome/browser/resources/downloads.js b/chrome/browser/resources/downloads.js
index 43023cf970f236a01f5a5a7113080823a61b2c17..3cbbe50d7ba021272adcf5afb9ddf177f94b075e 100644
--- a/chrome/browser/resources/downloads.js
+++ b/chrome/browser/resources/downloads.js
@@ -342,7 +342,8 @@ Download.DangerType = {
   NOT_DANGEROUS: "NOT_DANGEROUS",
   DANGEROUS_FILE: "DANGEROUS_FILE",
   DANGEROUS_URL: "DANGEROUS_URL",
-  DANGEROUS_CONTENT: "DANGEROUS_CONTENT"
+  DANGEROUS_CONTENT: "DANGEROUS_CONTENT",
+  UNCOMMON_CONTENT: "UNCOMMON_CONTENT"
 }
 
 /**
@@ -389,6 +390,9 @@ Download.prototype.update = function(download) {
     } else if (this.dangerType_ == Download.DangerType.DANGEROUS_CONTENT) {
       this.dangerDesc_.textContent = localStrings.getStringF(
           'danger_content_desc', this.fileName_);
+    } else if (this.dangerType_ == Download.DangerType.UNCOMMON_CONTENT) {
+      this.dangerDesc_.textContent = localStrings.getStringF(
+          'danger_uncommon_desc', this.fileName_);
     }
     this.danger_.style.display = 'block';
     this.safe_.style.display = 'none';