Make IPC task runner unfreezable for now

This CL reverts back a part of https://chromium-review.googlesource.com/c/chromium/src/+/1627834
and making IPC task runner unfreezable for now.
In the long run (after the next CL https://chromium-review.googlesource.com/c/chromium/src/+/1640738
is ready), it will be freezable again.
This is just to make sure that we are not breaking anything by making
the messages frozen.

Change-Id: I97f06320dd9c65c1bc73e08fca55ca4aa4bfcfe1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1642609Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Yuzu Saijo <yuzus@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665820}

content/renderer/render_thread_impl.cc

@@ -1065,7 +1065,8 @@ void RenderThreadImpl::AddRoute(int32_t routing_id, IPC::Listener* listener) {
     return;
 
   GetChannel()->AddListenerTaskRunner(
-      routing_id, frame->GetTaskRunner(blink::TaskType::kInternalFreezableIPC));
+      routing_id,
+      frame->GetTaskRunner(blink::TaskType::kInternalNavigationAssociated));
 
   scoped_refptr<PendingFrameCreate> create(it->second);
   frame->BindFrame(it->second->browser_info(), it->second->TakeFrameRequest());