Use TaskScheduler instead of blocking pool in mime_util.cc.

chrome/browser/extensions/api/file_handlers/mime_util.cc

Index: chrome/browser/extensions/api/file_handlers/mime_util.cc
diff --git a/chrome/browser/extensions/api/file_handlers/mime_util.cc b/chrome/browser/extensions/api/file_handlers/mime_util.cc
index 1f3207bd0cc32b31e490fe9488e7d5fd44864977..012bc954eb587b4585c877f132c04d544363b6a5 100644
--- a/chrome/browser/extensions/api/file_handlers/mime_util.cc
+++ b/chrome/browser/extensions/api/file_handlers/mime_util.cc
@@ -6,6 +6,7 @@
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
+#include "base/task_scheduler/post_task.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "chrome/browser/profiles/profile.h"
@@ -75,14 +76,13 @@ void OnGetMimeTypeFromMetadataForNonNativeLocalPathCompleted(
   std::unique_ptr<std::string> mime_type_from_extension(new std::string);
   std::string* const mime_type_from_extension_ptr =
       mime_type_from_extension.get();
-  BrowserThread::PostBlockingPoolTaskAndReply(
-      FROM_HERE,
-      base::Bind(base::IgnoreResult(&net::GetMimeTypeFromFile),
-                 local_path,
+  base::PostTaskWithTraitsAndReply(
+      FROM_HERE, base::TaskTraits().MayBlock().WithPriority(
+                     base::TaskPriority::BACKGROUND),

[benwells, 2017/02/14 06:03:21]

I think the priority for all of these should be USER_BLOCKING. For example,
these calls block the progress of opening files.

+      base::Bind(base::IgnoreResult(&net::GetMimeTypeFromFile), local_path,
                  mime_type_from_extension_ptr),
       base::Bind(&OnGetMimeTypeFromFileForNonNativeLocalPathCompleted,
-                 base::Passed(&mime_type_from_extension),
-                 callback));
+                 base::Passed(&mime_type_from_extension), callback));
 }
 #endif
 
@@ -119,12 +119,12 @@ void OnGetMimeTypeFromFileForNativeLocalPathCompleted(
   std::unique_ptr<std::string> sniffed_mime_type(
       new std::string(kMimeTypeApplicationOctetStream));
   std::string* const sniffed_mime_type_ptr = sniffed_mime_type.get();
-  BrowserThread::PostBlockingPoolTaskAndReply(
-      FROM_HERE,
+  base::PostTaskWithTraitsAndReply(
+      FROM_HERE, base::TaskTraits().MayBlock().WithPriority(
+                     base::TaskPriority::BACKGROUND),
       base::Bind(&SniffMimeType, local_path, sniffed_mime_type_ptr),
       base::Bind(&OnSniffMimeTypeForNativeLocalPathCompleted,
-                 base::Passed(&sniffed_mime_type),
-                 callback));
+                 base::Passed(&sniffed_mime_type), callback));
 }
 
 // Fetches MIME type for a local path and returns it with a |callback|.
@@ -152,15 +152,13 @@ void GetMimeTypeForLocalPath(
   std::unique_ptr<std::string> mime_type_from_extension(new std::string);
   std::string* const mime_type_from_extension_ptr =
       mime_type_from_extension.get();
-  BrowserThread::PostBlockingPoolTaskAndReply(
-      FROM_HERE,
-      base::Bind(base::IgnoreResult(&net::GetMimeTypeFromFile),
-                 local_path,
+  base::PostTaskWithTraitsAndReply(
+      FROM_HERE, base::TaskTraits().MayBlock().WithPriority(
+                     base::TaskPriority::BACKGROUND),
+      base::Bind(base::IgnoreResult(&net::GetMimeTypeFromFile), local_path,
                  mime_type_from_extension_ptr),
-      base::Bind(&OnGetMimeTypeFromFileForNativeLocalPathCompleted,
-                 local_path,
-                 base::Passed(&mime_type_from_extension),
-                 callback));
+      base::Bind(&OnGetMimeTypeFromFileForNativeLocalPathCompleted, local_path,
+                 base::Passed(&mime_type_from_extension), callback));
 }
 
 MimeTypeCollector::MimeTypeCollector(Profile* profile)