Change navigation preload initiatorType to "navigation"

As discussed at https://github.com/w3c/resource-timing/issues/110
the Resource Timing specification does not single out navigation
preload from other navigation types, and therefore the `initiatorType`
for it should be "navigation", rather than other.

This CL implements that change.

Intent-to-ship: https://groups.google.com/a/chromium.org/d/msg/blink-dev/W3InszDnV2k/AuJg4aAMDQAJ

Change-Id: Iba7fa038892936e164cd408355f1ac9f6592415b
Reviewed-on: https://chromium-review.googlesource.com/941342
Commit-Queue: Yoav Weiss <yoav@yoav.ws>
Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540483}

third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/navigation-preload/resource-timing.https.html

@@ -14,9 +14,9 @@ function check_timing_entry(entry, url, decodedBodySize, encodedBodySize) {
     'The entryType of preload response timing entry must be "resource' +
     '" :' + url);
   assert_equals(
-    entry.initiatorType, 'other',
+    entry.initiatorType, 'navigation',
     'The initiatorType of preload response timing entry must be ' +
-    '"other":' + url);
+    '"navigation":' + url);
 
   // If the server returns the redirect response, |decodedBodySize| is null and
   // |entry.decodedBodySize| shuld be 0. Otherwise |entry.decodedBodySize| must

third_party/WebKit/Source/modules/serviceworkers/FetchEvent.cpp

@@ -191,11 +191,10 @@ void FetchEvent::OnNavigationPreloadComplete(
   resource_response.SetEncodedDataLength(encoded_data_length);
   resource_response.SetEncodedBodyLength(encoded_body_length);
   resource_response.SetDecodedBodyLength(decoded_body_length);
-  // According to the current spec of Resource Timing, the initiator type of
-  // navigation preload request must be "other". But it may change when the spec
-  // discussion is settled. https://github.com/w3c/resource-timing/issues/110
+  // According to the Resource Timing spec, the initiator type of
+  // navigation preload request is "navigation".
   scoped_refptr<ResourceTimingInfo> info = ResourceTimingInfo::Create(
-      "other",
+      "navigation",
       TimeTicksInSeconds(
           resource_response.GetResourceLoadTiming()->RequestTime()),
       false /* is_main_resource */);