[Password Manager] Add UMA stats for custom passphrase users.

components/password_manager/core/browser/password_manager_client.h

Index: components/password_manager/core/browser/password_manager_client.h
diff --git a/components/password_manager/core/browser/password_manager_client.h b/components/password_manager/core/browser/password_manager_client.h
index a9c73bc86b9d1f3f6e58c1b191b7cebfa849cd0a..c2ffb4a1dbdc5052a75a2c456d8a57ef08606ae7 100644
--- a/components/password_manager/core/browser/password_manager_client.h
+++ b/components/password_manager/core/browser/password_manager_client.h
@@ -18,6 +18,11 @@ class PasswordFormManager;
 class PasswordManagerDriver;
 class PasswordStore;
 
+enum CustomPassphraseState {
+  WITHOUT_CUSTOM_PASSPHRASE,
+  ONLY_CUSTOM_PASSPHRASE
+};
+
 // An abstraction of operations that depend on the embedders (e.g. Chrome)
 // environment.
 class PasswordManagerClient {
@@ -39,6 +44,10 @@ class PasswordManagerClient {
   virtual bool ShouldFilterAutofillResult(
       const autofill::PasswordForm& form) = 0;
 
+  // Return the username that the user is syncing with. Should return an empty
+  // string if sync is not enabled for passwords.
+  virtual std::string GetSyncUsername() const = 0;
+
   // Returns true if |username| and |origin| correspond to the account which is
   // syncing.
   virtual bool IsSyncAccountCredential(
@@ -88,9 +97,10 @@ class PasswordManagerClient {
   virtual base::FieldTrial::Probability GetProbabilityForExperiment(
       const std::string& experiment_name);
 
-  // Returns true if password sync is enabled in the embedder. The default
-  // implementation returns false.
-  virtual bool IsPasswordSyncEnabled();
+  // Returns true if password sync is enabled in the embedder. Return value for
+  // custom passphrase users depends on |state|. The default implementation
+  // always returns false.
+  virtual bool IsPasswordSyncEnabled(CustomPassphraseState state);
 
   // Only for clients which registered with a LogRouter: If called with
   // |router_can_be_used| set to false, the client may no longer use the