Add new flag for consistent identity.

components/signin/core/common/signin_switches.h

Index: components/signin/core/common/signin_switches.h
diff --git a/components/signin/core/common/signin_switches.h b/components/signin/core/common/signin_switches.h
index 2e5dcbe96f1734c23ea4123f651aae82d275d021..ae624e3ce07aa166cd1c74dabd65df33e5f87199 100644
--- a/components/signin/core/common/signin_switches.h
+++ b/components/signin/core/common/signin_switches.h
@@ -7,9 +7,14 @@
 
 namespace switches {
 
+// These switches should not be queried from CommandLine::HasSwitch() directly.
+// Always go through the helper functions in profile_management_switches.h
+// to properly take into account the state of field trials.
+
 // All switches in alphabetical order. The switches should be documented
 // alongside the definition of their values in the .cc file.
 extern const char kClearTokenService[];
+extern const char kConsistentIdentity[];
 extern const char kEnableWebBasedSignin[];
 extern const char kExtensionsMultiAccount[];
 extern const char kFastUserSwitching[];