[TaskScheduler]: Use ScopedBlockingCall to mark blocking tasks.

This CL uses ScopedBlockingCall to mark blocking calls in /chrome/browser/resource_coordinator.

This CL was created by replacing calls to AssertBlockingAllowed()
with instantiations of ScopedBlockingCall(MAY_BLOCK).
I kindly ask the reviewer to 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/WILL_BLOCK). 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().

This CL was uploaded by git cl split.

R=fdoray@chromium.org

Bug: 874080
Change-Id: I5c943766529166e6f73470dbbcb426b1b182a37c
Reviewed-on: https://chromium-review.googlesource.com/1191190Reviewed-by: François Doray <fdoray@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586415}

chrome/browser/resource_coordinator/leveldb_site_characteristics_database.cc

@@ -14,7 +14,7 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/task_runner_util.h"
-#include "base/threading/thread_restrictions.h"
+#include "base/threading/scoped_blocking_call.h"
 #include "chrome/browser/resource_coordinator/utils.h"
 #include "third_party/leveldatabase/env_chromium.h"
 #include "third_party/leveldatabase/leveldb_chrome.h"
@@ -211,14 +211,18 @@ base::Optional<SiteCharacteristicsProto>
 LevelDBSiteCharacteristicsDatabase::AsyncHelper::ReadSiteCharacteristicsFromDB(
     const url::Origin& origin) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  base::AssertBlockingAllowed();
 
   if (!db_)
     return base::nullopt;
 
+  leveldb::Status s;
   std::string protobuf_value;
-  leveldb::Status s = db_->Get(
-      read_options_, SerializeOriginIntoDatabaseKey(origin), &protobuf_value);
+  {
+    base::ScopedBlockingCall scoped_blocking_call(
+        base::BlockingType::MAY_BLOCK);
+    s = db_->Get(read_options_, SerializeOriginIntoDatabaseKey(origin),
+                 &protobuf_value);
+  }
   base::Optional<SiteCharacteristicsProto> site_characteristic_proto;
   if (s.ok()) {
     site_characteristic_proto = SiteCharacteristicsProto();
@@ -236,14 +240,18 @@ void LevelDBSiteCharacteristicsDatabase::AsyncHelper::
         const url::Origin& origin,
         const SiteCharacteristicsProto& site_characteristic_proto) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  base::AssertBlockingAllowed();
 
   if (!db_)
     return;
 
-  leveldb::Status s =
-      db_->Put(write_options_, SerializeOriginIntoDatabaseKey(origin),
-               site_characteristic_proto.SerializeAsString());
+  leveldb::Status s;
+  {
+    base::ScopedBlockingCall scoped_blocking_call(
+        base::BlockingType::MAY_BLOCK);
+    s = db_->Put(write_options_, SerializeOriginIntoDatabaseKey(origin),
+                 site_characteristic_proto.SerializeAsString());
+  }
+
   if (!s.ok()) {
     DLOG(ERROR)
         << "Error while inserting an element in the site characteristics "
@@ -255,11 +263,11 @@ void LevelDBSiteCharacteristicsDatabase::AsyncHelper::
     RemoveSiteCharacteristicsFromDB(
         const std::vector<url::Origin>& site_origins) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  base::AssertBlockingAllowed();
 
   if (!db_)
     return;
 
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
   leveldb::WriteBatch batch;
   for (const auto& iter : site_origins)
     batch.Delete(SerializeOriginIntoDatabaseKey(iter));
@@ -272,12 +280,12 @@ void LevelDBSiteCharacteristicsDatabase::AsyncHelper::
 
 void LevelDBSiteCharacteristicsDatabase::AsyncHelper::ClearDatabase() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  base::AssertBlockingAllowed();
   if (!db_)
     return;
 
-  leveldb_env::Options options;
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
   db_.reset();
+  leveldb_env::Options options;
   leveldb::Status status = leveldb::DestroyDB(db_path_.AsUTF8Unsafe(), options);
   if (status.ok()) {
     OpenOrCreateDatabaseImpl();
@@ -291,7 +299,7 @@ LevelDBSiteCharacteristicsDatabase::AsyncHelper::OpeningType
 LevelDBSiteCharacteristicsDatabase::AsyncHelper::OpenOrCreateDatabaseImpl() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(!db_) << "Database already open";
-  base::AssertBlockingAllowed();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 
   OpeningType opening_type = OpeningType::kNewDb;