[Passwords] Preview fill for Touch To Fill

This change implements highlighting the username and password field that
are about to be filled in by Touch To Fill.

Bug: 1013182
Change-Id: I778dddef757641aede49c682e83da69606313dbc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1859979Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705906}

chrome/renderer/autofill/password_autofill_agent_browsertest.cc

@@ -1718,6 +1718,8 @@ TEST_F(PasswordAutofillAgentTest, TryToShowTouchToFillUsername) {
   EXPECT_TRUE(
       password_autofill_agent_->TryToShowTouchToFill(username_element_));
   EXPECT_TRUE(password_autofill_agent_->ShouldSuppressKeyboard());
+  EXPECT_EQ(WebAutofillState::kPreviewed, username_element_.GetAutofillState());
+  EXPECT_EQ(WebAutofillState::kPreviewed, password_element_.GetAutofillState());
 
   EXPECT_CALL(fake_driver_, ShowTouchToFill);
   base::RunLoop().RunUntilIdle();
@@ -1729,6 +1731,7 @@ TEST_F(PasswordAutofillAgentTest, TryToShowTouchToFillPassword) {
   EXPECT_TRUE(
       password_autofill_agent_->TryToShowTouchToFill(password_element_));
   EXPECT_TRUE(password_autofill_agent_->ShouldSuppressKeyboard());
+  EXPECT_EQ(WebAutofillState::kPreviewed, password_element_.GetAutofillState());
 
   EXPECT_CALL(fake_driver_, ShowTouchToFill);
   base::RunLoop().RunUntilIdle();
@@ -1745,19 +1748,23 @@ TEST_F(PasswordAutofillAgentTest, DontTryToShowTouchToFillReadonlyPassword) {
 TEST_F(PasswordAutofillAgentTest, TouchToFillDismissed) {
   SimulateOnFillPasswordForm(fill_data_);
 
+  auto previous_state = password_element_.GetAutofillState();
   // Touch to fill will be shown multiple times until TouchToFillDismissed()
   // gets called.
   EXPECT_TRUE(
       password_autofill_agent_->TryToShowTouchToFill(password_element_));
   EXPECT_TRUE(password_autofill_agent_->ShouldSuppressKeyboard());
+  EXPECT_EQ(WebAutofillState::kPreviewed, password_element_.GetAutofillState());
 
   EXPECT_CALL(fake_driver_, ShowTouchToFill);
   base::RunLoop().RunUntilIdle();
 
+  // Make sure that resetting Touch To Fill resets the Autofill state.
   password_autofill_agent_->TouchToFillDismissed();
   EXPECT_FALSE(
       password_autofill_agent_->TryToShowTouchToFill(password_element_));
   EXPECT_FALSE(password_autofill_agent_->ShouldSuppressKeyboard());
+  EXPECT_EQ(previous_state, password_element_.GetAutofillState());
 
   // Reload the page and simulate fill.
   LoadHTML(kFormHTML);
@@ -1769,6 +1776,7 @@ TEST_F(PasswordAutofillAgentTest, TouchToFillDismissed) {
   EXPECT_TRUE(
       password_autofill_agent_->TryToShowTouchToFill(password_element_));
   EXPECT_TRUE(password_autofill_agent_->ShouldSuppressKeyboard());
+  EXPECT_EQ(WebAutofillState::kPreviewed, password_element_.GetAutofillState());
 
   EXPECT_CALL(fake_driver_, ShowTouchToFill);
   base::RunLoop().RunUntilIdle();

components/autofill/content/renderer/password_autofill_agent.cc

@@ -784,20 +784,33 @@ bool PasswordAutofillAgent::TryToShowTouchToFill(
   if (touch_to_fill_state_ != TouchToFillState::kShouldShow)
     return false;
 
-  const WebInputElement* element = ToWebInputElement(&control_element);
+  const WebInputElement* input_element = ToWebInputElement(&control_element);
   WebInputElement username_element;
   WebInputElement password_element;
   PasswordInfo* password_info = nullptr;
-  if (!element ||
-      !FindPasswordInfoForElement(*element, &username_element,
+  if (!input_element ||
+      !FindPasswordInfoForElement(*input_element, &username_element,
                                   &password_element, &password_info)) {
     return false;
   }
 
-  DCHECK(!password_element.IsNull());
-  if (!IsElementEditable(password_element))
+  // Don't trigger Touch To Fill when there is no password element or it is not
+  // editable.
+  if (password_element.IsNull() || !IsElementEditable(password_element))
     return false;
 
+  // Highlight the fields that are about to be filled by the user and remember
+  // the old autofill state of |username_element| and |password_element|.
+  if (IsUsernameAmendable(username_element,
+                          input_element->IsPasswordFieldForAutofill())) {
+    username_autofill_state_ = username_element.GetAutofillState();
+    username_element.SetAutofillState(WebAutofillState::kPreviewed);
+  }
+
+  password_autofill_state_ = password_element.GetAutofillState();
+  password_element.SetAutofillState(WebAutofillState::kPreviewed);
+
+  focused_input_element_ = *input_element;
   GetPasswordManagerDriver()->ShowTouchToFill();
   touch_to_fill_state_ = TouchToFillState::kIsShowing;
   return true;
@@ -1208,6 +1221,24 @@ void PasswordAutofillAgent::SetLoggingState(bool active) {
 
 void PasswordAutofillAgent::TouchToFillDismissed() {
   touch_to_fill_state_ = TouchToFillState::kWasShown;
+
+  // Clear the autofill state from the username and password element. Note that
+  // we don't make use of ClearPreview() here, since this is considering the
+  // elements' SuggestedValue(), which Touch To Fill does not set.
+  DCHECK(!focused_input_element_.IsNull());
+  WebInputElement username_element;
+  WebInputElement password_element;
+  PasswordInfo* password_info = nullptr;
+  if (!FindPasswordInfoForElement(focused_input_element_, &username_element,
+                                  &password_element, &password_info)) {
+    return;
+  }
+
+  if (!username_element.IsNull())
+    username_element.SetAutofillState(username_autofill_state_);
+
+  if (!password_element.IsNull())
+    password_element.SetAutofillState(password_autofill_state_);
 }
 
 void PasswordAutofillAgent::AnnotateFieldsWithParsingResult(