Use fake Input Device Settings with chrome://device-emulator

chrome/browser/chromeos/system/input_device_settings.h

Index: chrome/browser/chromeos/system/input_device_settings.h
diff --git a/chrome/browser/chromeos/system/input_device_settings.h b/chrome/browser/chromeos/system/input_device_settings.h
index da1945861c68b801f8bc92fc0383d4326bbc4bd7..4c4895c706cd13bf2c1839f4c91c052f693c7523 100644
--- a/chrome/browser/chromeos/system/input_device_settings.h
+++ b/chrome/browser/chromeos/system/input_device_settings.h
@@ -14,6 +14,7 @@ class PrefRegistrySimple;
 namespace chromeos {
 namespace system {
 
+class FakeInputDeviceSettings;
 class InputDeviceSettings;
 
 namespace internal {
@@ -160,10 +161,13 @@ class CHROMEOS_EXPORT InputDeviceSettings {
   // Returns current instance of InputDeviceSettings.
   static InputDeviceSettings* Get();
 
+  // Returns test instance of InputDeviceSettings.
+  static FakeInputDeviceSettings* GetForTesting();

[stevenjb, 2016/06/30 00:17:30]

See my comment in the other CL, this should be merged into Get(). Let me know if
that is more problematic than I imagine.

[michaelpg, 2016/07/01 22:01:48]

I would have to git try that to make sure it doesn't break anything else in
CrOS.

But the reason I made GetForTesting() was to use the setters (eg
set_mouse_exists)
which are specific to FakeInputDeviceSettings.

I could create a new FakeInputDeviceSettings and use SetSettingsForTesting in
device_emulator_message_handler.cc, but then opening chrome://device-emulator
would reset those settings, which doesn't make sense.

[stevenjb, 2016/07/02 00:28:26]

I agree we shouldn't create a new / additional FakeInputDeviceSettings. That
should be transparent.

Take a look at FakeShillServiceClient::GetTestInterface. This is a model we have
used to allow setting of fake properties without having to expose the details of
the fake class to callers. The fake implementation will return a valid fake
interface and the real implementation will return a null interface.

[michaelpg, 2016/07/07 22:16:54]

Done, created InputDeviceSettings::FakeInterface. Definitely simpler.

+
   // Replaces current instance with |test_settings|. Takes ownership of
   // |test_settings|. Default implementation could be returned back by passing
   // NULL to this method.
-  static void SetSettingsForTesting(InputDeviceSettings* test_settings);
+  static void SetSettingsForTesting(FakeInputDeviceSettings* test_settings);
 
   // Returns true if UI should implement enhanced keyboard support for cases
   // where other input devices like mouse are absent.
@@ -179,8 +183,8 @@ class CHROMEOS_EXPORT InputDeviceSettings {
   void ToggleTouchscreen();
   void ToggleTouchpad();
 
-  // Calls |callback| asynchronously after determining if a touchpad is
-  // connected.
+  // Calls |callback|, possibly asynchronously, after determining if a touchpad
+  // is connected.
   virtual void TouchpadExists(const DeviceExistsCallback& callback) = 0;
 
   // Updates several touchpad settings at a time. Updates only settings that
@@ -204,7 +208,8 @@ class CHROMEOS_EXPORT InputDeviceSettings {
   // Turns natural scrolling on/off for all devices except wheel mice
   virtual void SetNaturalScroll(bool enabled) = 0;
 
-  // Calls |callback| asynchronously after determining if a mouse is connected.
+  // Calls |callback|, possibly asynchronously, after determining if a mouse is
+  // connected.
   virtual void MouseExists(const DeviceExistsCallback& callback) = 0;
 
   // Updates several mouse settings at a time. Updates only settings that