[TaskScheduler]: Use ScopedBlockingCall to mark blocking tasks.

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

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=rouslan@chromium.org

Bug: 874080
Change-Id: I82ae2e1ea937cce2e4bc815ac66f236081b82960
Reviewed-on: https://chromium-review.googlesource.com/1191531Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587290}

chrome/browser/spellchecker/spellcheck_custom_dictionary.cc

@@ -18,7 +18,7 @@
 #include "base/strings/string_util.h"
 #include "base/task/post_task.h"
 #include "base/task_runner_util.h"
-#include "base/threading/thread_restrictions.h"
+#include "base/threading/scoped_blocking_call.h"
 #include "chrome/common/chrome_constants.h"
 #include "components/spellcheck/browser/spellcheck_host_metrics.h"
 #include "components/spellcheck/common/spellcheck_common.h"
@@ -63,11 +63,14 @@ enum ChangeSanitationResult {
 // invalid checksum, then returns ChecksumStatus::INVALID and clears |words|.
 ChecksumStatus LoadFile(const base::FilePath& file_path,
                         std::set<std::string>* words) {
-  base::AssertBlockingAllowed();
   DCHECK(words);
   words->clear();
   std::string contents;
-  base::ReadFileToString(file_path, &contents);
+  {
+    base::ScopedBlockingCall scoped_blocking_call(
+        base::BlockingType::MAY_BLOCK);
+    base::ReadFileToString(file_path, &contents);
+  }
   size_t pos = contents.rfind(CHECKSUM_PREFIX);
   if (pos != std::string::npos) {
     std::string checksum = contents.substr(pos + strlen(CHECKSUM_PREFIX));
@@ -122,7 +125,6 @@ int SanitizeWordsToAdd(const std::set<std::string>& existing,
 // called on the file thread.
 std::unique_ptr<SpellcheckCustomDictionary::LoadFileResult>
 LoadDictionaryFileReliably(const base::FilePath& path) {
-  base::AssertBlockingAllowed();
   // Load the contents and verify the checksum.
   std::unique_ptr<SpellcheckCustomDictionary::LoadFileResult> result(
       new SpellcheckCustomDictionary::LoadFileResult);
@@ -144,22 +146,24 @@ LoadDictionaryFileReliably(const base::FilePath& path) {
 // the custom spellcheck dictionary at |path|.
 void SaveDictionaryFileReliably(const base::FilePath& path,
                                 const std::set<std::string>& custom_words) {
-  base::AssertBlockingAllowed();
   std::stringstream content;
   for (const std::string& word : custom_words)
     content << word << '\n';
 
   std::string checksum = base::MD5String(content.str());
   content << CHECKSUM_PREFIX << checksum;
-  base::CopyFile(path, path.AddExtension(BACKUP_EXTENSION));
-  base::ImportantFileWriter::WriteFileAtomically(path, content.str());
+  {
+    base::ScopedBlockingCall scoped_blocking_call(
+        base::BlockingType::MAY_BLOCK);
+    base::CopyFile(path, path.AddExtension(BACKUP_EXTENSION));
+    base::ImportantFileWriter::WriteFileAtomically(path, content.str());
+  }
 }
 
 void SavePassedWordsToDictionaryFileReliably(
     const base::FilePath& path,
     std::unique_ptr<SpellcheckCustomDictionary::LoadFileResult>
         load_file_result) {
-  base::AssertBlockingAllowed();
   DCHECK(load_file_result);
   SaveDictionaryFileReliably(path, load_file_result->words);
 }
@@ -391,7 +395,6 @@ SpellcheckCustomDictionary::LoadFileResult::~LoadFileResult() {}
 // static
 std::unique_ptr<SpellcheckCustomDictionary::LoadFileResult>
 SpellcheckCustomDictionary::LoadDictionaryFile(const base::FilePath& path) {
-  base::AssertBlockingAllowed();
   std::unique_ptr<LoadFileResult> result = LoadDictionaryFileReliably(path);
   SpellCheckHostMetrics::RecordCustomWordCountStats(result->words.size());
   return result;
@@ -401,7 +404,6 @@ SpellcheckCustomDictionary::LoadDictionaryFile(const base::FilePath& path) {
 void SpellcheckCustomDictionary::UpdateDictionaryFile(
     std::unique_ptr<Change> dictionary_change,
     const base::FilePath& path) {
-  base::AssertBlockingAllowed();
   DCHECK(dictionary_change);
 
   if (dictionary_change->empty())

chrome/browser/spellchecker/spellcheck_hunspell_dictionary.cc

@@ -16,7 +16,7 @@
 #include "base/single_thread_task_runner.h"
 #include "base/task/post_task.h"
 #include "base/task_runner_util.h"
-#include "base/threading/thread_restrictions.h"
+#include "base/threading/scoped_blocking_call.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "chrome/browser/spellchecker/spellcheck_service.h"
@@ -49,7 +49,7 @@ base::LazyInstance<GURL>::Leaky g_download_url_for_testing =
 
 // Close the file.
 void CloseDictionary(base::File file) {
-  base::AssertBlockingAllowed();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
   file.Close();
 }
 
@@ -57,7 +57,7 @@ void CloseDictionary(base::File file) {
 // returns false.
 bool SaveDictionaryData(std::unique_ptr<std::string> data,
                         const base::FilePath& path) {
-  base::AssertBlockingAllowed();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 
   size_t bytes_written =
       base::WriteFile(path, data->data(), data->length());
@@ -318,7 +318,7 @@ void SpellcheckHunspellDictionary::DownloadDictionary(GURL url) {
 // static
 SpellcheckHunspellDictionary::DictionaryFile
 SpellcheckHunspellDictionary::OpenDictionaryFile(const base::FilePath& path) {
-  base::AssertBlockingAllowed();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 
   // The default_dictionary_file can either come from the standard list of
   // hunspell dictionaries (determined in InitializeDictionaryLocation), or it
@@ -370,7 +370,7 @@ SpellcheckHunspellDictionary::OpenDictionaryFile(const base::FilePath& path) {
 SpellcheckHunspellDictionary::DictionaryFile
 SpellcheckHunspellDictionary::InitializeDictionaryLocation(
     const std::string& language) {
-  base::AssertBlockingAllowed();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 
   // The default place where the spellcheck dictionary resides is
   // chrome::DIR_APP_DICTIONARIES.