cros: Fix crostini uninstall calling dbus on wrong thread

Bug: 962884
Change-Id: Ia6ce88211926c4ccb6726f3aab9e8677e196d6f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1612851Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Reviewed-by: Xiaochu Liu <xiaochu@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659979}

chrome/browser/component_updater/cros_component_installer_chromeos.cc

@@ -21,6 +21,7 @@
 #include "chromeos/dbus/image_loader_client.h"
 #include "components/component_updater/component_updater_paths.h"
 #include "components/crx_file/id_util.h"
+#include "content/public/browser/browser_task_traits.h"
 #include "content/public/browser/browser_thread.h"
 #include "crypto/sha2.h"
 
@@ -61,6 +62,13 @@ const ComponentConfig* FindConfig(const std::string& name) {
 // TODO(xiaochu): add metrics for component usage (https://crbug.com/793052).
 void LogCustomUninstall(base::Optional<bool> result) {}
 
+void FinishCustomUninstallOnUIThread(const std::string& name) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  chromeos::DBusThreadManager::Get()->GetImageLoaderClient()->UnmountComponent(
+      name, base::BindOnce(&LogCustomUninstall));
+}
+
 std::string GenerateId(const std::string& sha2hashstr) {
   // kIdSize is the count of a pair of hex in the sha2hash array.
   // In string representation of sha2hash, size is doubled since each hex is
@@ -144,8 +152,9 @@ CrOSComponentInstallerPolicy::OnCustomInstall(
 void CrOSComponentInstallerPolicy::OnCustomUninstall() {
   cros_component_installer_->UnregisterCompatiblePath(name_);
 
-  chromeos::DBusThreadManager::Get()->GetImageLoaderClient()->UnmountComponent(
-      name_, base::BindOnce(&LogCustomUninstall));
+  base::PostTaskWithTraits(
+      FROM_HERE, {content::BrowserThread::UI},
+      base::BindOnce(&FinishCustomUninstallOnUIThread, name_));
 }
 
 void CrOSComponentInstallerPolicy::ComponentReady(

components/component_updater/component_installer.h

@@ -65,6 +65,7 @@ class ComponentInstallerPolicy {
   // OnCustomUninstall is called during the unregister (uninstall) process.
   // Components that require custom uninstallation operations should implement
   // them here.
+  // Called only from a thread belonging to a blocking thread pool.
   virtual void OnCustomUninstall() = 0;
 
   // ComponentReady is called in two cases: