[Password Generation] Sends CSS classes inside autofill proto

components/autofill/core/browser/proto/server.proto

Index: components/autofill/core/browser/proto/server.proto
diff --git a/components/autofill/core/browser/proto/server.proto b/components/autofill/core/browser/proto/server.proto
index 46bbfdb8ff88b8f27ecd927eaeacfc005560faaf..5e6a9b7e2afc3f7788eac0a160ace75838de8935 100644
--- a/components/autofill/core/browser/proto/server.proto
+++ b/components/autofill/core/browser/proto/server.proto
@@ -34,7 +34,7 @@ message AutofillQueryResponseContents {
 
 // This message contains information about the field types in a single form.
 // It is sent by the toolbar to contribute to the field type statistics.
-// Next available id: 19
+// Next available id: 20
 message AutofillUploadContents {
   required string client_version = 1;
   required fixed64 form_signature = 2;
@@ -91,6 +91,9 @@ message AutofillUploadContents {
     }
     // The outcome of HTML parsing based form classifier.
     optional FormClassifierOutcome form_classifier_outcome = 18;
+
+    // The value of the class attribute on the field, if present.
+    optional string css_classes = 19;
   }
   // Signature of the form action host (e.g. Hash64Bit("example.com")).
   optional fixed64 action_signature = 13;