[iOS] Removing ChromeIdentityService::GetIdentityWithEmail()

ChromeIdentityService::GetIdentityWithEmail() is unused.

The implementation is removed with:
crrev.com/i/3318008.

Change-Id: I8926f60be9bfd18814b1fc2aaadf4a3f9321c5dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2455607Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815077}

ios/public/provider/chrome/browser/signin/chrome_identity_service.h

@@ -155,10 +155,6 @@ class ChromeIdentityService {
   // identitites.
   virtual bool IsValidIdentity(ChromeIdentity* identity);
 
-  // Returns the chrome identity having the email equal to |email| or |nil| if
-  // no matching identity is found.
-  virtual ChromeIdentity* GetIdentityWithEmail(const std::string& email);
-
   // Returns the chrome identity having the gaia ID equal to |gaia_id| or |nil|
   // if no matching identity is found.
   virtual ChromeIdentity* GetIdentityWithGaiaID(const std::string& gaia_id);

ios/public/provider/chrome/browser/signin/chrome_identity_service.mm

@@ -65,11 +65,6 @@ bool ChromeIdentityService::IsValidIdentity(ChromeIdentity* identity) {
   return false;
 }
 
-ChromeIdentity* ChromeIdentityService::GetIdentityWithEmail(
-    const std::string& email) {
-  return nil;
-}
-
 ChromeIdentity* ChromeIdentityService::GetIdentityWithGaiaID(
     const std::string& gaia_id) {
   return nil;