Allow the PrinterDetector to be constructed with a delegated profile.

The add printer dialog was crashing in Guest Mode because a
PrinterDetector could not be constructed.  It is okay for
PrinterDetector to be shared between logged in profiles.

BUG=724278

Review-Url: https://codereview.chromium.org/2898833002
Cr-Commit-Position: refs/heads/master@{#473761}

chrome/browser/chromeos/printer_detector/printer_detector_factory.cc

@@ -7,6 +7,7 @@
 #include "base/command_line.h"
 #include "chrome/browser/chromeos/printer_detector/printer_detector.h"
 #include "chrome/browser/chromeos/printing/printers_manager_factory.h"
+#include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/chrome_switches.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
@@ -43,6 +44,11 @@ PrinterDetectorFactory::PrinterDetectorFactory()
 PrinterDetectorFactory::~PrinterDetectorFactory() {
 }
 
+content::BrowserContext* PrinterDetectorFactory::GetBrowserContextToUse(
+    content::BrowserContext* context) const {
+  return chrome::GetBrowserContextRedirectedInIncognito(context);
+}
+
 KeyedService* PrinterDetectorFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(

chrome/browser/chromeos/printer_detector/printer_detector_factory.h

@@ -24,11 +24,17 @@ class PrinterDetectorFactory : public BrowserContextKeyedServiceFactory {
 
   PrinterDetector* Get(content::BrowserContext* context);
 
+ protected:
+  // BrowserContextKeyedServiceFactory:
+  content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const override;
+
  private:
   friend struct base::LazyInstanceTraitsBase<PrinterDetectorFactory>;
   PrinterDetectorFactory();
   ~PrinterDetectorFactory() override;
 
+  // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* browser_context) const override;
   bool ServiceIsCreatedWithBrowserContext() const override;