[scheduler] Do not use kInternalIPC in modules/content_index

Remove kInternalIPC task type.
- If it's used to bind associated interface, use
  kInternalNavigationAssociated instead.
- If it's used to bind non-associated interface, use the task source
  mentioned in the spec, kMiscPlatformAPI if it's not speced yet or
  kInternalDefault if it's a non-spec-related task.

R=falken@chromium.org,peter@chromium.org

Change-Id: Id82556a9da16d0d04acdaf4eed7a9604e8796172
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1891290Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711675}

third_party/blink/renderer/modules/content_index/service_worker_registration_content_index.cc

@@ -39,9 +39,10 @@ ContentIndex* ServiceWorkerRegistrationContentIndex::index(
 ContentIndex* ServiceWorkerRegistrationContentIndex::index() {
   if (!content_index_) {
     ExecutionContext* execution_context = registration_->GetExecutionContext();
+    // TODO(falken): Consider defining a task source in the spec for this event.
     content_index_ = MakeGarbageCollected<ContentIndex>(
         registration_,
-        execution_context->GetTaskRunner(TaskType::kInternalIPC));
+        execution_context->GetTaskRunner(TaskType::kMiscPlatformAPI));
   }
 
   return content_index_.Get();