Allow the PrinterDetector to be constructed with a delegated profile.

chrome/browser/chromeos/printer_detector/printer_detector_factory.h

Index: chrome/browser/chromeos/printer_detector/printer_detector_factory.h
diff --git a/chrome/browser/chromeos/printer_detector/printer_detector_factory.h b/chrome/browser/chromeos/printer_detector/printer_detector_factory.h
index 252cba9d11a971cfb7f0eaf3144ef434cb554481..da0abea27a789714c30771781eb2ea1c6bba38a3 100644
--- a/chrome/browser/chromeos/printer_detector/printer_detector_factory.h
+++ b/chrome/browser/chromeos/printer_detector/printer_detector_factory.h
@@ -24,6 +24,10 @@ class PrinterDetectorFactory : public BrowserContextKeyedServiceFactory {
 
   PrinterDetector* Get(content::BrowserContext* context);
 
+ protected:
+  content::BrowserContext* GetBrowserContextToUse(

[Daniel Erat, 2017/05/22 22:29:37]

nit: mind adding a comment above this line to make it easier to see where this
is overridden from? (yes, there's only one base class in this case.) these
styles are common in chromium:

  // BrowserContextKeyedServiceFactory:

or

  // BrowserContextKeyedServiceFactory overrides:

ditto for the overridden methods in the private section.

[skau, 2017/05/22 23:49:11]

Done.

+      content::BrowserContext* context) const override;
+
  private:
   friend struct base::LazyInstanceTraitsBase<PrinterDetectorFactory>;
   PrinterDetectorFactory();