[ios] Compare ChromeIdentity by value

Ensuring ChromeIdentity uniqueness is currently thread-usafe. Removing
the uniqueness guaranty requires that code correctly uses -isEqual: to
compare identities by value instead of doing the comparison of pointers
(like you use -isStringEqual: to compare NSString).

After doing an audit of all code using ChromeIdentity, convert all the
comparison that were using pointers comparison instead of -isEqual:.

Bug: none
Change-Id: I110cb8e289ccaf482dd7addf67f5d194aed98a75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2139666
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757463}

ios/chrome/browser/ui/authentication/signin_promo_view_mediator.mm

@@ -594,7 +594,7 @@ const char* AlreadySeenSigninViewPreferenceKey(
   if (identities.count != 0) {
     newIdentity = identities[0];
   }
-  if (newIdentity != _defaultIdentity) {
+  if (![_defaultIdentity isEqual:newIdentity]) {
     [self selectIdentity:newIdentity];
     [self sendConsumerNotificationWithIdentityChanged:YES];
   }

ios/chrome/browser/ui/authentication/unified_consent/identity_chooser/identity_chooser_mediator.mm

@@ -42,7 +42,7 @@
 }
 
 - (void)setSelectedIdentity:(ChromeIdentity*)selectedIdentity {
-  if (_selectedIdentity == selectedIdentity)
+  if ([_selectedIdentity isEqual:selectedIdentity])
     return;
   IdentityChooserItem* previousSelectedItem = [self.consumer
       identityChooserItemWithGaiaID:self.selectedIdentity.gaiaID];

ios/chrome/browser/ui/authentication/unified_consent/unified_consent_mediator.mm

@@ -51,7 +51,7 @@
 }
 
 - (void)setSelectedIdentity:(ChromeIdentity*)selectedIdentity {
-  if (selectedIdentity == self.selectedIdentity) {
+  if ([self.selectedIdentity isEqual:selectedIdentity]) {
     return;
   }
   // nil is allowed only if there is no other identity.
@@ -145,7 +145,7 @@
 }
 
 - (void)profileUpdate:(ChromeIdentity*)identity {
-  if (identity == self.selectedIdentity) {
+  if ([self.selectedIdentity isEqual:identity]) {
     [self updateViewController];
   }
 }

ios/chrome/browser/ui/settings/settings_table_view_controller.mm

@@ -1168,7 +1168,7 @@ NSString* kDevViewSourceKey = @"DevViewSource";
 #pragma mark ChromeIdentityServiceObserver
 
 - (void)profileUpdate:(ChromeIdentity*)identity {
-  if (identity == _identity) {
+  if ([_identity isEqual:identity]) {
     [self reloadAccountCell];
   }
 }