[Extensions][Task Scheduler] Remove ExtensionService::GetFileTaskRunner

ExtensionService::GetFileTaskRunner() now just forwards to returning
extensions::GetExtensionFileTaskRunner() (the devoted sequenced task
runner for extension-related file tasks). Update callers to just use
this instead to avoid confusion and simplify the code, as well as
remove unneeded dependencies on ExtensionService.

Bug: 750122

Change-Id: Ic0d6a6ddc087d211d7c9290287e2698b7898ea4a
Reviewed-on: https://chromium-review.googlesource.com/598946
Reviewed-by: Evan Stade <[email protected]>
Reviewed-by: Istiaque Ahmed <[email protected]>
Reviewed-by: Toni Barzic <[email protected]>
Commit-Queue: Devlin <[email protected]>
Cr-Commit-Position: refs/heads/master@{#493218}
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index 95ca0f3..f46cbae 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -563,7 +563,7 @@
     // Delete extension_path since we're not creating a CrxInstaller
     // that would do it for us.
     if (file_ownership_passed &&
-        !GetFileTaskRunner()->PostTask(
+        !extensions::GetExtensionFileTaskRunner()->PostTask(
             FROM_HERE, base::BindOnce(&extensions::file_util::DeleteFile,
                                       file.path, false)))
       NOTREACHED();
@@ -821,7 +821,7 @@
 
   // Tell the backend to start deleting installed extensions on the file thread.
   if (!Manifest::IsUnpackedLocation(extension->location())) {
-    if (!GetFileTaskRunner()->PostTask(
+    if (!extensions::GetExtensionFileTaskRunner()->PostTask(
             FROM_HERE,
             base::BindOnce(&ExtensionService::UninstallExtensionOnFileThread,
                            extension->id(), profile_, install_directory_,
@@ -1772,7 +1772,7 @@
 
       // Delete the extension directory since we're not going to
       // load it.
-      if (!GetFileTaskRunner()->PostTask(
+      if (!extensions::GetExtensionFileTaskRunner()->PostTask(
               FROM_HERE, base::BindOnce(&extensions::file_util::DeleteFile,
                                         extension->path(), true))) {
         NOTREACHED();
@@ -2508,12 +2508,6 @@
   }
 }
 
-base::SequencedTaskRunner* ExtensionService::GetFileTaskRunner() {
-  // TODO(devlin): Update callers to use GetExtensionFileTaskRunner()
-  // directly.
-  return extensions::GetExtensionFileTaskRunner().get();
-}
-
 // Used only by test code.
 void ExtensionService::UnloadAllExtensionsInternal() {
   profile_->GetExtensionSpecialStoragePolicy()->RevokeRightsForAllExtensions();