[BrowserThread] Remove DCHECK which invokes ExtractBrowserThreadId()

This is preventing the migration of callers that use BrowserTaskTraits
specific traits when invoking GetUIThreadTaskRunner() @
https://chromium-review.googlesource.com/c/chromium/src/+/2211138/8

R=altimin@chromium.org

Bug: 1026641
Change-Id: I098daf92d861447049315332f42d2d53fae15d1a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2212992Reviewed-by: Alexander Timin <altimin@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Auto-Submit: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771845}

content/browser/scheduler/browser_task_executor.cc

@@ -96,10 +96,6 @@ BaseBrowserTaskExecutor::CreateCOMSTATaskRunner(
 scoped_refptr<base::SingleThreadTaskRunner>
 BaseBrowserTaskExecutor::GetTaskRunner(BrowserThread::ID identifier,
                                        const base::TaskTraits& traits) const {
-  DCHECK(traits.extension_id() ==
-             base::TaskTraitsExtensionStorage::kInvalidExtensionId ||
-         ExtractBrowserThreadId(traits) == identifier);
-
   const QueueType queue_type = GetQueueType(traits);
 
   switch (identifier) {

content/browser/scheduler/browser_task_executor_unittest.cc

@@ -120,6 +120,16 @@ TEST_F(BrowserTaskExecutorTest, RunAllPendingTasksForTestingOnIOIsReentrant) {
   BrowserTaskExecutor::RunAllPendingTasksOnThreadForTesting(BrowserThread::IO);
 }
 
+TEST_F(BrowserTaskExecutorTest, GetTaskRunnerWithBrowserTaskTraits) {
+  StrictMockTask task_1;
+
+  GetUIThreadTaskRunner({BrowserTaskType::kPreconnect})
+      ->PostTask(FROM_HERE, task_1.Get());
+
+  EXPECT_CALL(task_1, Run);
+  BrowserTaskExecutor::RunAllPendingTasksOnThreadForTesting(BrowserThread::UI);
+}
+
 // Helper to perform the same tets for all BrowserThread::ID values.
 class BrowserTaskTraitsMappingTest : public BrowserTaskExecutorTest {
  protected: