Add "previewing on hover" support for password field.

components/autofill/core/browser/autofill_driver.h

Index: components/autofill/core/browser/autofill_driver.h
diff --git a/components/autofill/core/browser/autofill_driver.h b/components/autofill/core/browser/autofill_driver.h
index 629d85f8a5bbf8c51f30935df4a2d116e1574eba..a3109cc22cb8b407dddc2fd2d1da7491494217cc 100644
--- a/components/autofill/core/browser/autofill_driver.h
+++ b/components/autofill/core/browser/autofill_driver.h
@@ -73,6 +73,11 @@ class AutofillDriver {
   virtual void RendererShouldAcceptPasswordAutofillSuggestion(
       const base::string16& username) = 0;
 
+  // Tells the renderer to preview the password autofill suggestion for
+  // |username|.
+  virtual void RendererShouldPreviewPassword(
+      const base::string16& username) = 0;
+
   // Tells the renderer to clear the currently filled Autofill results.
   virtual void RendererShouldClearFilledForm() = 0;