Don't make query impressions for favicon requests, a=chris

diff --git a/src/controllers/SearchController.php b/src/controllers/SearchController.php
index 6609e8e0a..a8e1a3bd2 100755
--- a/src/controllers/SearchController.php
+++ b/src/controllers/SearchController.php
@@ -155,8 +155,11 @@ class SearchController extends Controller implements CrawlConstants
                 }
                 $this->cacheRequestAndOutput($arg, $ui_array, $query,
                     $index_timestamp);
-                $this->model("impression")->addQueryImpression(
-                    "cache:$arg");
+                if (empty($ui_array['field']) ||
+                    $ui_array['field'] != 'favicon') {
+                    $this->model("impression")->addQueryImpression(
+                        "cache:$arg");
+                }
                 return;
             }
         }