[Autofill] Add Chrome flag that annotates web forms with form and field signatures

components/autofill/content/renderer/password_autofill_agent.cc

Index: components/autofill/content/renderer/password_autofill_agent.cc
diff --git a/components/autofill/content/renderer/password_autofill_agent.cc b/components/autofill/content/renderer/password_autofill_agent.cc
index aee3f94116bd88b2d321da9d06828be675d15112..5c2ade82e0320fd2c0d1198c0c62de58937ac1ec 100644
--- a/components/autofill/content/renderer/password_autofill_agent.cc
+++ b/components/autofill/content/renderer/password_autofill_agent.cc
@@ -12,11 +12,13 @@
 #include <vector>
 
 #include "base/bind.h"
+#include "base/command_line.h"
 #include "base/i18n/case_conversion.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ -25,6 +27,7 @@
 #include "components/autofill/content/renderer/password_form_conversion_utils.h"
 #include "components/autofill/content/renderer/renderer_save_password_progress_logger.h"
 #include "components/autofill/core/common/autofill_constants.h"
+#include "components/autofill/core/common/autofill_switches.h"
 #include "components/autofill/core/common/autofill_util.h"
 #include "components/autofill/core/common/form_field_data.h"
 #include "components/autofill/core/common/password_form_fill_data.h"
@@ -60,6 +63,9 @@ static const size_t kMaximumTextSizeForAutocomplete = 1000;
 const char kDummyUsernameField[] = "anonymous_username";
 const char kDummyPasswordField[] = "anonymous_password";
 
+const char kDebugAttributeForFormSignature[] = "form_signature";
+const char kDebugAttributeForFieldSignature[] = "field_signature";
+
 // Maps element names to the actual elements to simplify form filling.
 typedef std::map<base::string16, blink::WebInputElement> FormInputElementMap;
 
@@ -562,6 +568,37 @@ bool FillFormOnPasswordReceived(
       field_value_and_properties_map, registration_callback, logger);
 }
 
+// Annotate |forms| with form and field signatures as HTML attributes.
+void AnnotateFormsWithSignatures(
+    blink::WebVector<blink::WebFormElement> forms) {
+  for (blink::WebFormElement form : forms) {
+    std::unique_ptr<PasswordForm> password_form(
+        CreatePasswordFormFromWebForm(form, nullptr, nullptr));
+    if (password_form) {
+      form.setAttribute(
+          blink::WebString::fromASCII(kDebugAttributeForFormSignature),
+          blink::WebString::fromUTF8(base::Uint64ToString(
+              CalculateFormSignature(password_form->form_data))));
+
+      blink::WebVector<blink::WebFormControlElement> control_elements =
+          form_util::ExtractAutofillableElementsInForm(form);
+      DCHECK(control_elements.size() == password_form->form_data.fields.size());
+      for (size_t i = 0; i < control_elements.size(); ++i) {
+        blink::WebFormControlElement& control_element = control_elements[i];
+        if (!form_util::IsAutofillableElement(control_element))
+          continue;
+
+        const FormFieldData& field = password_form->form_data.fields[i];
+        DCHECK(field.name == control_element.nameForAutofill().utf16());
+        control_element.setAttribute(
+            blink::WebString::fromASCII(kDebugAttributeForFieldSignature),
+            blink::WebString::fromUTF8(
+                base::Uint64ToString(CalculateFieldSignatureForField(field))));
+      }
+    }
+  }
+}
+
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1016,6 +1053,10 @@ void PasswordAutofillAgent::SendPasswordForms(bool only_visible) {
 
   blink::WebVector<blink::WebFormElement> forms;
   frame->document().forms(forms);
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kShowAutofillSignatures)) {
+    AnnotateFormsWithSignatures(forms);
+  }
   if (logger)
     logger->LogNumber(Logger::STRING_NUMBER_OF_ALL_FORMS, forms.size());