Record the initial state of the Physical Web at startup

ios/chrome/browser/physical_web/start_physical_web_discovery.mm

Index: ios/chrome/browser/physical_web/start_physical_web_discovery.mm
diff --git a/ios/chrome/browser/physical_web/start_physical_web_discovery.mm b/ios/chrome/browser/physical_web/start_physical_web_discovery.mm
index f1b492e337f08485a902588ac4f1b08299e5097c..196b78c9538660550500952e82bb51721e830852 100644
--- a/ios/chrome/browser/physical_web/start_physical_web_discovery.mm
+++ b/ios/chrome/browser/physical_web/start_physical_web_discovery.mm
@@ -11,6 +11,7 @@
 #import "ios/chrome/browser/experimental_flags.h"
 #import "ios/chrome/browser/geolocation/omnibox_geolocation_config.h"
 #include "ios/chrome/browser/physical_web/physical_web_constants.h"
+#import "ios/chrome/browser/physical_web/physical_web_initial_state_recorder.h"
 #include "ios/chrome/browser/pref_names.h"
 #include "url/gurl.h"
 
@@ -26,17 +27,27 @@ void StartPhysicalWebDiscovery(PrefService* pref_service, bool is_incognito) {
   // send the X-Geo geolocation header in search queries to www.google.com.
   int preference_state =
       pref_service->GetInteger(prefs::kIosPhysicalWebEnabled);
-  if (preference_state == physical_web::kPhysicalWebOnboarding) {
-    // Check that Location Services is enabled.
-    bool location_services_enabled =
-        [CLLocationManager locationServicesEnabled];
 
-    // Check that the user has authorized Chrome to use location.
-    CLAuthorizationStatus auth_status = [CLLocationManager authorizationStatus];
-    bool location_authorized =
-        auth_status == kCLAuthorizationStatusAuthorizedWhenInUse ||
-        auth_status == kCLAuthorizationStatusAuthorizedAlways;
+  // Check that Location Services is enabled.
+  bool location_services_enabled = [CLLocationManager locationServicesEnabled];
+
+  // Check that the user has authorized Chrome to use location.
+  CLAuthorizationStatus auth_status = [CLLocationManager authorizationStatus];
+  bool location_authorized =
+      auth_status == kCLAuthorizationStatusAuthorizedWhenInUse ||
+      auth_status == kCLAuthorizationStatusAuthorizedAlways;
 
+  // Record the initial state of Bluetooth, location, and the Physical Web
+  // preference the first time discovery is started.
+  static dispatch_once_t once_token;
+  dispatch_once(&once_token, ^{
+    [[[PhysicalWebInitialStateRecorder alloc]
+        initWithPreferenceState:preference_state
+        locationServicesEnabled:location_services_enabled
+             locationAuthorized:location_authorized] autorelease];

[mattreynolds, 2016/10/27 23:56:04]

Not sure if this is kosher. The idea is to let the
PhysicalWebInitialStateRecorder take ownership of itself so it can self-destruct
once the asynchronous Bluetooth check is complete and the histogram is recorded.

[rohitrao (ping after 24h), 2016/10/31 19:41:08]

I think this works, but I don't really like it.  This feels like it will be way
too easy for someone to accidentally turn into a leak or a crash in the future.

[mattreynolds, 2016/11/01 17:17:17]

Agreed, I'd rather not leave it like this. The reason I designed it this way is
because I couldn't figure out how else to get the preference state and the
bluetooth enabled state in the same place. The bluetooth check is async, so we
need someone to hold a reference to the bluetooth delegate until it gets its
response. To get the preference, we need a valid PrefService.

I think I could move this into the PhysicalWebDataSource if I could get the
PrefService from a global context. Is that possible, or do I need a
BrowserState?

+  });
+
+  if (preference_state == physical_web::kPhysicalWebOnboarding) {
     // Check that the user has not revoked the geolocation permission for
     // Google.
     bool geolocation_eligible = [[OmniboxGeolocationConfig sharedInstance]