[TaskScheduler]: Migrate off of AssertBlockingAllowedDeprecated in /chrome/browser/extensions

base::AssertBlockingAllowedDeprecated is deprecated in favor of
ScopedBlockingCall, which serves as a precise annotation of
the scope that may/will block.

Please make sure of the following:
  - ScopedBlockingCall is instantiated in a scope with minimal CPU usage.
    If this is not the case, ScopedBlockingCall should be instantiated
    closer to the blocking call. See scoped_blocking_call.h for more
    info. Please let me know when/where the blocking call happens if this needs
    to be changed.
  - Parameter |blocking_type| matches expectation:
      MAY_BLOCK: The call might block (e.g. file I/O that might hit in memory cache).
      WILL_BLOCK: The call will definitely block (e.g. cache already checked and now pinging
        server synchronously).
    See BlockingType for more info. While I assumed MAY_BLOCK by default, that might
    not be the best fit if we know that this callsite is guaranteed to block.
  - The ScopedBlockingCall's scope covers the entirety of the blocking operation
    previously asserted against by the AssertBlockingAllowed().
  - Calls to blocking //base APIs don't need to be annotated
    with ScopedBlockingCall. All blocking //base APIs (e.g. base::ReadFileToString, base::File::Read,
    base::SysInfo::AmountOfFreeDiskSpace, base::WaitableEvent::Wait, etc.) have their
    own internal annotations.

Refer to the top-level CL if necessary :
https://chromium-review.googlesource.com/c/chromium/src/+/1338391

Please CQ if LGTY!

This CL was uploaded by git cl split.

R=finnur@chromium.org

Bug: 903957
Change-Id: I461f534870c60e1fc6b9c1c441d388cc99646c10
Reviewed-on: https://chromium-review.googlesource.com/c/1338483Reviewed-by: Finnur Thorarinsson <finnur@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611279}

chrome/browser/extensions/external_pref_loader.cc

@@ -43,8 +43,6 @@ constexpr base::FilePath::CharType kExternalExtensionJson[] =
 
 std::set<base::FilePath> GetPrefsCandidateFilesFromFolder(
       const base::FilePath& external_extension_search_path) {
-  base::AssertBlockingAllowedDeprecated();
-
   std::set<base::FilePath> external_extension_paths;
 
   if (!base::PathExists(external_extension_search_path)) {
@@ -235,8 +233,6 @@ ExternalPrefLoader::ExtractExtensionPrefs(base::ValueDeserializer* deserializer,
 }
 
 void ExternalPrefLoader::LoadOnFileThread() {
-  base::AssertBlockingAllowedDeprecated();
-
   auto prefs = std::make_unique<base::DictionaryValue>();
 
   // TODO(skerner): Some values of base_path_id_ will cause
@@ -273,7 +269,6 @@ void ExternalPrefLoader::LoadOnFileThread() {
 
 void ExternalPrefLoader::ReadExternalExtensionPrefFile(
     base::DictionaryValue* prefs) {
-  base::AssertBlockingAllowedDeprecated();
   CHECK(NULL != prefs);
 
   base::FilePath json_file = base_path_.Append(kExternalExtensionJson);
@@ -311,7 +306,6 @@ void ExternalPrefLoader::ReadExternalExtensionPrefFile(
 
 void ExternalPrefLoader::ReadStandaloneExtensionPrefFiles(
     base::DictionaryValue* prefs) {
-  base::AssertBlockingAllowedDeprecated();
   CHECK(NULL != prefs);
 
   // First list the potential .json candidates.

chrome/browser/extensions/external_registry_loader_win.cc

@@ -16,7 +16,6 @@
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/task/post_task.h"
-#include "base/threading/thread_restrictions.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "base/version.h"
@@ -79,7 +78,6 @@ void ExternalRegistryLoader::StartLoading() {
 
 std::unique_ptr<base::DictionaryValue>
 ExternalRegistryLoader::LoadPrefsOnBlockingThread() {
-  base::AssertBlockingAllowedDeprecated();
   auto prefs = std::make_unique<base::DictionaryValue>();
 
   // A map of IDs, to weed out duplicates between HKCU and HKLM.

chrome/browser/extensions/unpacked_installer.cc

@@ -14,7 +14,6 @@
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/task/post_task.h"
-#include "base/threading/thread_restrictions.h"
 #include "chrome/browser/extensions/extension_management.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/load_error_reporter.h"
@@ -241,8 +240,6 @@ int UnpackedInstaller::GetFlags() {
 bool UnpackedInstaller::LoadExtension(Manifest::Location location,
                                       int flags,
                                       std::string* error) {
-  base::AssertBlockingAllowedDeprecated();
-
   // Clean up the kMetadataFolder if necessary. This prevents spurious
   // warnings/errors and ensures we don't treat a user provided file as one by
   // the Extension system.
@@ -267,7 +264,6 @@ bool UnpackedInstaller::LoadExtension(Manifest::Location location,
 
 bool UnpackedInstaller::IndexAndPersistRulesIfNeeded(std::string* error) {
   DCHECK(extension());
-  base::AssertBlockingAllowedDeprecated();
 
   const ExtensionResource* resource =
       declarative_net_request::DNRManifestData::GetRulesetResource(extension());
@@ -301,8 +297,6 @@ bool UnpackedInstaller::IsLoadingUnpackedAllowed() const {
 }
 
 void UnpackedInstaller::GetAbsolutePath() {
-  base::AssertBlockingAllowedDeprecated();
-
   extension_path_ = base::MakeAbsoluteFilePath(extension_path_);
 
   base::PostTaskWithTraits(
@@ -326,8 +320,6 @@ void UnpackedInstaller::CheckExtensionFileAccess() {
 }
 
 void UnpackedInstaller::LoadWithFileAccess(int flags) {
-  base::AssertBlockingAllowedDeprecated();
-
   std::string error;
   if (!LoadExtension(Manifest::UNPACKED, flags, &error)) {
     base::PostTaskWithTraits(

chrome/browser/extensions/webstore_installer.cc

@@ -25,7 +25,6 @@
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/task/post_task.h"
-#include "base/threading/thread_restrictions.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "chrome/browser/chrome_notification_types.h"
@@ -113,7 +112,6 @@ base::FilePath* g_download_directory_for_tests = NULL;
 
 base::FilePath GetDownloadFilePath(const base::FilePath& download_directory,
                                    const std::string& id) {
-  base::AssertBlockingAllowedDeprecated();
   // Ensure the download directory exists. TODO(asargent) - make this use
   // common code from the downloads system.
   if (!base::DirectoryExists(download_directory) &&