Move impl of identity.GetAccounts() extension API to its own file

chrome/browser/extensions/api/identity/identity_api.h

Index: chrome/browser/extensions/api/identity/identity_api.h
diff --git a/chrome/browser/extensions/api/identity/identity_api.h b/chrome/browser/extensions/api/identity/identity_api.h
index b4976c59bd18d41eed5d92a22570be968eafe0cf..751cc5a385249e2f5c6be7785a58d4e501d62249 100644
--- a/chrome/browser/extensions/api/identity/identity_api.h
+++ b/chrome/browser/extensions/api/identity/identity_api.h
@@ -18,6 +18,7 @@
 #include "build/build_config.h"
 #include "chrome/browser/extensions/api/identity/extension_token_key.h"
 #include "chrome/browser/extensions/api/identity/gaia_web_auth_flow.h"
+#include "chrome/browser/extensions/api/identity/identity_get_accounts_function.h"
 #include "chrome/browser/extensions/api/identity/identity_get_auth_token_function.h"
 #include "chrome/browser/extensions/api/identity/identity_get_profile_user_info_function.h"
 #include "chrome/browser/extensions/api/identity/identity_launch_web_auth_flow_function.h"
@@ -133,20 +134,6 @@ class IdentityAPI : public BrowserContextKeyedAPI,
 template <>
 void BrowserContextKeyedAPIFactory<IdentityAPI>::DeclareFactoryDependencies();
 
-class IdentityGetAccountsFunction : public ChromeUIThreadExtensionFunction {
- public:
-  DECLARE_EXTENSION_FUNCTION("identity.getAccounts",
-                             IDENTITY_GETACCOUNTS);
-
-  IdentityGetAccountsFunction();
-
- private:
-  ~IdentityGetAccountsFunction() override;
-
-  // UIThreadExtensionFunction implementation.
-  ExtensionFunction::ResponseAction Run() override;
-};
-
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_IDENTITY_IDENTITY_API_H_