Implement updateViaCache flag and no-cache by default for main service worker scripts

content/browser/service_worker/service_worker_database.proto

Index: content/browser/service_worker/service_worker_database.proto
diff --git a/content/browser/service_worker/service_worker_database.proto b/content/browser/service_worker/service_worker_database.proto
index 892001d00c0b94865b7c3f068984b62b5365fbe2..adc319b3da27cf6c9af7d1e6b23085cf97d4ab9c 100644
--- a/content/browser/service_worker/service_worker_database.proto
+++ b/content/browser/service_worker/service_worker_database.proto
@@ -23,6 +23,13 @@ message ServiceWorkerNavigationPreloadState {
 }
 
 message ServiceWorkerRegistrationData {
+  enum ServiceWorkerUpdateViaCacheType {
+    UNKNOWN = 0;

[nhiroki, 2017/08/04 09:24:50]

I wonder if we don't have to have UNKNOWN type because we shouldn't write a
registration data to the DB if its cache type is "UNKNOWN".

[yuryu, 2017/08/17 07:36:35]

Done.

+    IMPORTS = 1;
+    ALL = 2;
+    NONE = 3;
+  }
+
   required int64 registration_id = 1;
   required string scope_url = 2;
   required string script_url = 3;
@@ -54,6 +61,9 @@ message ServiceWorkerRegistrationData {
   // The set of features that the worker used up until the time installation
   // completed. The values must be from blink::UseCounter::Feature enum.
   repeated uint32 used_features = 13;
+
+  optional ServiceWorkerUpdateViaCacheType update_via_cache = 14
+      [default = IMPORTS];
 }
 
 message ServiceWorkerResourceRecord {