[scheduler] Add unthrottled-by-blockable task queue to fix touch latency regression.

third_party/WebKit/Source/web/tests/scheduler/ThrottlingTest.cpp

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code if governed by a BSD-style license that can be
 // found in LICENSE file.
 
 #include "platform/scheduler/child/web_scheduler.h"
 #include "platform/testing/RuntimeEnabledFeaturesTestHelpers.h"
 #include "platform/testing/UnitTestHelpers.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebThread.h"
 #include "public/platform/scheduler/renderer/renderer_scheduler.h"
@@ skipping 50 matching lines @@
   // Run delayed tasks for 1 second. All tasks should be completed
   // with throttling disabled.
   testing::RunDelayedTasks(1000);
 
   EXPECT_THAT(ConsoleMessages(), ElementsAre("called f", "called f", "called f",
                                              "called f", "called f"));
 }
 
 class BackgroundRendererThrottlingTest : public SimTest {};
 
-TEST_F(BackgroundRendererThrottlingTest, BackgroundRenderersAreThrottled) {
+TEST_F(BackgroundRendererThrottlingTest,
+       DISABLED_BackgroundRenderersAreThrottled) {
   SimRequest main_resource("https://example.com/", "text/html");
 
   LoadURL("https://example.com/");
 
   main_resource.Complete(
       "(<script>"
       "  function f(repetitions) {"
       "     if (repetitions == 0) return;"
       "     console.log('called f');"
       "     setTimeout(f, 10, repetitions - 1);"
       "  }"
       "  setTimeout(f, 10, 3);"
       "</script>)");
 
   Platform::Current()
       ->CurrentThread()
       ->Scheduler()
       ->GetRendererSchedulerForTest()
       ->OnRendererBackgrounded();
 
   // Make sure that we run a task once a second.
   for (int i = 0; i < 3; ++i) {
     testing::RunDelayedTasks(1000);
     EXPECT_THAT(ConsoleMessages(), ElementsAre("called f"));
     ConsoleMessages().clear();
   }
 }
 
 }  // namespace blink