Reland "Safety check: add tests for the Chrome cleaner child backend"

This is a reland of 9d1db5b8
Fixes the missing import and constant.

Original change's description:
> Safety check: add tests for the Chrome cleaner child backend
>
> * Test that each possible CCT status results in the corresponding
>   safety check child status and display string.
> * Test that CCT being enterprise managed is handled correctly.
>
> Bug: 1087263
> Change-Id: I84d93408800cb4fbe8d138578c586a0ae89dbfc9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2249980
> Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
> Reviewed-by: Joe Mason <joenotcharles@chromium.org>
> Commit-Queue: Rainhard Findling <rainhard@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#783942}

Bug: 1087263
Change-Id: Iddb785080835e437517c7adba7eacaec20356ca6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2279752Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Reviewed-by: Joe Mason <joenotcharles@chromium.org>
Commit-Queue: Rainhard Findling <rainhard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#785664}

chrome/browser/safe_browsing/chrome_cleaner/chrome_cleaner_controller_impl_win.cc

@@ -281,6 +281,11 @@ void ChromeCleanerControllerImpl::SetStateForTesting(State state) {
     idle_reason_ = IdleReason::kInitial;
 }
 
+void ChromeCleanerControllerImpl::SetIdleForTesting(IdleReason idle_reason) {
+  state_ = State::kIdle;
+  idle_reason_ = idle_reason;
+}
+
 // static
 void ChromeCleanerControllerImpl::ResetInstanceForTesting() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);

chrome/browser/safe_browsing/chrome_cleaner/chrome_cleaner_controller_impl_win.h

@@ -84,6 +84,7 @@ class ChromeCleanerControllerImpl : public ChromeCleanerController {
   // Force the current controller's state for tests that check the effect of
   // starting and completing reporter runs.
   void SetStateForTesting(State state);
+  void SetIdleForTesting(IdleReason idle_reason);
 
  private:
   ChromeCleanerControllerImpl();