Move definition of PasswordType enum to a separate header.

components/sync/core/sync_encryption_handler.h

Index: components/sync/core/sync_encryption_handler.h
diff --git a/components/sync/core/sync_encryption_handler.h b/components/sync/core/sync_encryption_handler.h
index 3eb46046e9caefc4728d1e86c2b3512455df4be1..09a6298e734764db28de5812a0db41eded95e402 100644
--- a/components/sync/core/sync_encryption_handler.h
+++ b/components/sync/core/sync_encryption_handler.h
@@ -14,6 +14,7 @@
 namespace syncer {
 
 class Cryptographer;
+enum class PassphraseType;
 
 // Reasons due to which Cryptographer might require a passphrase.
 enum PassphraseRequiredReason {
@@ -27,18 +28,6 @@ enum PassphraseRequiredReason {
                                        // decryption.
 };
 
-// The different states for the encryption passphrase. These control if and how
-// the user should be prompted for a decryption passphrase.
-// Do not re-order or delete these entries; they are used in a UMA histogram.
-// Please edit SyncPassphraseType in histograms.xml if a value is added.
-enum class PassphraseType {
-  IMPLICIT_PASSPHRASE = 0,         // GAIA-based passphrase (deprecated).
-  KEYSTORE_PASSPHRASE = 1,         // Keystore passphrase.
-  FROZEN_IMPLICIT_PASSPHRASE = 2,  // Frozen GAIA passphrase.
-  CUSTOM_PASSPHRASE = 3,           // User-provided passphrase.
-  PASSPHRASE_TYPE_SIZE,            // The size of this enum; keep last.
-};
-
 // Enum used to distinguish which bootstrap encryption token is being updated.
 enum BootstrapTokenType {
   PASSPHRASE_BOOTSTRAP_TOKEN,