Use a per-frame task runner at GuestViewContainer

This CL switches task runners at several places from per-thread to
per-frame. The purpose of this change is to make it possible to freeze
tasks for bfcache.

We found an actual case that JavaScript is executed:
browser_tests --gtest_filter=WebViewScrollGuestContentBrowserPluginSpecificTest.OverscrollControllerSeesConsumedScrollsInGuest

Bug: 870606
Change-Id: I34d1cb8b94955798a896e741b76135dec6f8c031
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1530314Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Kevin McNee <mcnee@chromium.org>
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642360}

components/guest_view/renderer/guest_view_container.cc

@@ -7,7 +7,6 @@
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/macros.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "components/guest_view/common/guest_view_constants.h"
 #include "components/guest_view/common/guest_view_messages.h"
 #include "components/guest_view/renderer/guest_view_request.h"
@@ -248,8 +247,9 @@ void GuestViewContainer::DidResizeElement(const gfx::Size& new_size) {
   if (element_resize_callback_.IsEmpty())
     return;
 
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, base::BindOnce(&GuestViewContainer::CallElementResizeCallback,
+  render_frame_->GetTaskRunner(blink::TaskType::kInternalDefault)
+      ->PostTask(FROM_HERE,
+                 base::BindOnce(&GuestViewContainer::CallElementResizeCallback,
                                 weak_ptr_factory_.GetWeakPtr(), new_size));
 }