Migrate off base::ThreadPool()-as-a-trait in /chrome/browser/extensions

This CL is a logical no-op.

It manually covers the use cases the script
(https://crbug.com/1026641#c22) didn't cover in
https://chromium-review.googlesource.com/c/chromium/src/+/2026350.

A few of the affected files were also migrated to
content::GetUIThreadTaskRunner() whenever surrounding code consistency
was at stake (but the bulk of that migration is staged to happen after
this one so this wasn't a priority in this batch).

Most files intentionally kept base/task/post_task.h as an include. It is
still required because of a cyclical dependency during the migration
preventing base/task/thread_pool.h from implicitly providing
base/task/task_traits.h to its users (callers that explicitly store
TaskTraits and include task_traits.h don't have this problem). The
post_task.h include will be cleaned up in a later phase.

This CL was uploaded by git cl split.

R=reillyg@chromium.org

Bug: 1026641
Change-Id: I781bcf648308b5583f5d85308ee0383b7f69be02
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2078420
Commit-Queue: Gabriel Charette <gab@chromium.org>
Auto-Submit: Gabriel Charette <gab@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745499}

chrome/browser/extensions/api/image_writer_private/image_writer_utility_client_browsertest.cc

@@ -219,8 +219,8 @@ class ImageWriterUtilityClientTest : public InProcessBrowserTest {
 
   base::SequencedTaskRunner* CreateTaskRunner() {
     DCHECK(!task_runner_.get());
-    task_runner_ =
-        base::CreateSequencedTaskRunner(Operation::blocking_task_traits());
+    task_runner_ = base::ThreadPool::CreateSequencedTaskRunner(
+        Operation::blocking_task_traits());
     return task_runner_.get();
   }
 

chrome/browser/extensions/api/image_writer_private/operation.cc

@@ -9,6 +9,7 @@
 #include "base/bind.h"
 #include "base/files/file_util.h"
 #include "base/task/post_task.h"
+#include "base/task/thread_pool.h"
 #include "build/build_config.h"
 #include "chrome/browser/extensions/api/image_writer_private/error_messages.h"
 #include "chrome/browser/extensions/api/image_writer_private/operation_manager.h"
@@ -42,7 +43,8 @@ Operation::Operation(base::WeakPtr<OperationManager> manager,
       stage_(image_writer_api::STAGE_UNKNOWN),
       progress_(0),
       download_folder_(download_folder),
-      task_runner_(base::CreateSequencedTaskRunner(blocking_task_traits())) {
+      task_runner_(
+          base::ThreadPool::CreateSequencedTaskRunner(blocking_task_traits())) {
 }
 
 Operation::~Operation() {

chrome/browser/extensions/api/image_writer_private/operation.h

@@ -229,7 +229,6 @@ class Operation : public base::RefCountedThreadSafe<Operation> {
 
   static constexpr base::TaskTraits blocking_task_traits() {
     return {
-        base::ThreadPool(),
         // Requires I/O.
         base::MayBlock(),
         // Apps (e.g. Chromebook Recovery Utility) present UI feedback based on

chrome/browser/extensions/api/page_capture/page_capture_api.cc

@@ -53,7 +53,6 @@ const char kPageCaptureNotAllowed[] =
 const char kUserDenied[] = "User denied request.";
 #endif
 constexpr base::TaskTraits kCreateTemporaryFileTaskTraits = {
-    base::ThreadPool(),
     // Requires IO.
     base::MayBlock(),
 
@@ -127,7 +126,7 @@ ExtensionFunction::ResponseAction PageCaptureSaveAsMHTMLFunction::Run() {
   if (!CanCaptureCurrentPage(&error)) {
     return RespondNow(Error(error));
   }
-  base::PostTask(
+  base::ThreadPool::PostTask(
       FROM_HERE, kCreateTemporaryFileTaskTraits,
       base::BindOnce(&PageCaptureSaveAsMHTMLFunction::CreateTemporaryFile,
                      this));
@@ -188,7 +187,7 @@ bool PageCaptureSaveAsMHTMLFunction::OnMessageReceived(
 void PageCaptureSaveAsMHTMLFunction::ResolvePermissionRequest(
     const PermissionIDSet& allowed_permissions) {
   if (allowed_permissions.ContainsID(APIPermission::kPageCapture)) {
-    base::PostTask(
+    base::ThreadPool::PostTask(
         FROM_HERE, kCreateTemporaryFileTaskTraits,
         base::BindOnce(&PageCaptureSaveAsMHTMLFunction::CreateTemporaryFile,
                        this));