Fallback to infer text behind <input>s for assigned labels.

A developer can associate a <label> to an input in two ways:
1) Using the for-attribute: <label for=fieldID>
2) By making the <input> a child of the <label>.

This CL addresses the second case. Right now, FindChildText() is used
to extract the content of the label. However, FindChildText() stops at
autofillable elements, which causes us to miss the label in cases like
this:
<label>
  <input>
  text
</label>
This causes problems e.g. on citilink.ru (see https://chromium-review.googlesource.com/c/chromium/src/+/4079457/comment/de5c03ad_a1d9971a/).

Generally, this behaviour of FindChildText() seems reasonable, since
text behind an input is oftentimes only relevant for error handling etc.
However, in case the input is explicitly associated with the label, it
might make sense to be more lenient.

This CL adds a fallback mechanism: If extracting a label using
FindChildText() for an associated label of the second kind fails,
we instead look at the text after the input.

Change-Id: I20a69ede53f65ce3f255a2fd7450f4a0e8365d26
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4106611
Reviewed-by: Dominic Battré <battre@chromium.org>
Commit-Queue: Florian Leimgruber <fleimgruber@google.com>
Cr-Commit-Position: refs/heads/main@{#1084877}

chrome/renderer/autofill/form_autofill_browsertest.cc

@@ -3592,6 +3592,23 @@ TEST_F(FormAutofillTest, LabelForAttribute) {
       testing::UnorderedElementsAre(base::Bucket(AssignedLabelSource::kId, 2)));
 }
 
+// Tests that when a label is assigned to an input, text behind it is considered
+// as a fallback.
+// The label is assigned to the input without the for-attribute, by declaring it
+// it inside the label.
+TEST_F(FormAutofillTest, LabelTextBehindInput) {
+  ExpectLabels(R"(
+    <form name=TestForm action=http://cnn.com>
+      <label>
+        <input>
+        label
+      </label>
+    </form>
+  )",
+               /*id_attributes=*/{u""}, /*name_attributes=*/{u""},
+               /*labels=*/{u"label"}, /*names=*/{u""}, /*values=*/{u""});
+}
+
 TEST_F(FormAutofillTest, LabelsWithSpans) {
   ExpectJohnSmithLabelsAndIdAttributes(
       "<FORM name='TestForm' action='http://cnn.com' method='post'>"

components/autofill/content/renderer/form_autofill_util.cc

@@ -1396,12 +1396,33 @@ void MatchLabelsAndFields(
       field_data = iter->first;
     }
 
+    // Skip `label` if we could not find an associated form control.
     if (!field_data)
       continue;
 
     std::u16string label_text = FindChildText(label);
-    if (label_text.empty())
-      continue;
+    if (label_text.empty()) {
+      if (label.HasAttribute(*kFor)) {
+        continue;
+      }
+      DCHECK(!control.IsNull() && control.IsFormControlElement());
+      // An associated form control was found, but the `label` does not have a
+      // for-attribute, so the form control must be a descendant of the `label`.
+      // Since `FindChildText()` stops at autofillable elements, the
+      // `label_text` can be empty if the "text" is declared behind the <input>.
+      // For example:
+      // <label>
+      //  <input>
+      //  text
+      // </label>
+      // Thus, consider text behind the <input> as a fallback.
+      // Since associated labels are counted as `kFor`, the source is ignored.
+      FormFieldData::LabelSource irrelevant_source;
+      if (!InferLabelFromNext(control.To<WebFormControlElement>(), label_text,
+                              irrelevant_source)) {
+        continue;
+      }
+    }
 
     // Concatenate labels because some sites might have multiple label
     // candidates.

components/autofill/ios/form_util/resources/fill.js

@@ -729,7 +729,10 @@ function matchLabelsAndFields_(
     if (!('label' in fieldData)) {
       fieldData['label'] = '';
     }
-    const labelText = __gCrWeb.fill.findChildText(label);
+    let labelText = __gCrWeb.fill.findChildText(label);
+    if (labelText.length === 0 && !label.htmlFor) {
+      labelText = __gCrWeb.fill.inferLabelFromNext(fieldElement);
+    }
     // Concatenate labels because some sites might have multiple label
     // candidates.
     if (fieldData['label'].length > 0 && labelText.length > 0) {

components/test/data/autofill/heuristics/output/047_register_continental.com.out

@@ -8,8 +8,8 @@ NAME_FIRST | ctl00$ContentInfo$Name$FName$txtFName | First Name: |  | ctl00$Cust
 NAME_MIDDLE_INITIAL | ctl00$ContentInfo$Name$MName$txtMName | Middle Initial (optional): |  | ctl00$CustomerHeader$ddlCountries_1
 NAME_LAST | ctl00$ContentInfo$Name$LName$txtLName | Last Name: |  | ctl00$CustomerHeader$ddlCountries_1
 UNKNOWN_TYPE | ctl00$ContentInfo$Name$suffix$txtSuffix | Suffix (optional): |  | ctl00$CustomerHeader$ddlCountries_1
-UNKNOWN_TYPE | ctl00$ContentInfo$MemberAge$EnrollmentAge | This OnePass account is for an adult 18 years of age or older. | rdoAdult | ctl00$CustomerHeader$ddlCountries_1
-UNKNOWN_TYPE | ctl00$ContentInfo$MemberAge$EnrollmentAge | This OnePass account is for a minor under the age of 18. | rdoMinor | ctl00$CustomerHeader$ddlCountries_1
+UNKNOWN_TYPE | ctl00$ContentInfo$MemberAge$EnrollmentAge | This OnePass account is for an adult 18 years of age or older. This OnePass account is for an adult 18 years of age or older. | rdoAdult | ctl00$CustomerHeader$ddlCountries_1
+UNKNOWN_TYPE | ctl00$ContentInfo$MemberAge$EnrollmentAge | This OnePass account is for a minor under the age of 18. This OnePass account is for a minor under the age of 18. | rdoMinor | ctl00$CustomerHeader$ddlCountries_1
 UNKNOWN_TYPE | ctl00$ContentInfo$BirthDate$txtDOB | Minor’s Date of Birth: | mm/dd/yyyy | ctl00$CustomerHeader$ddlCountries_1
 UNKNOWN_TYPE | ctl00$ContentInfo$AddressType$AddressType | Home | rdoAddTypeHome | ctl00$CustomerHeader$ddlCountries_1
 UNKNOWN_TYPE | ctl00$ContentInfo$AddressType$AddressType | Business/Other | rdoAddTypeBusiness | ctl00$CustomerHeader$ddlCountries_1

components/test/data/autofill/heuristics/output/111_checkout_virgin_america.com.out

@@ -1,10 +1,10 @@
-UNKNOWN_TYPE | creditCard | American Express Discover |  | creditCard_1
-CREDIT_CARD_NAME_FULL | cardholderName | Cardholder's name |  | cardholderName_2
-CREDIT_CARD_EXP_MONTH | expireMonth | Expiration Date |  | cardholderName_2
-CREDIT_CARD_EXP_4_DIGIT_YEAR | expireYear | Expiration Date |  | cardholderName_2
-CREDIT_CARD_VERIFICATION_CODE | securityNumber | CVV Number 3 or 4 digit number |  | cardholderName_2
-UNKNOWN_TYPE | nickname | Card's nickname e.g. My Visa, Corporate card, etc |  | creditCard_1
-UNKNOWN_TYPE | useAddress | Use stored address | use-stored-address | creditCard_1
-UNKNOWN_TYPE | stored-address |  | ? | creditCard_1
-UNKNOWN_TYPE | useAddress | Add new address | add-new-address | creditCard_1
-UNKNOWN_TYPE | shouldSave | Save credit card info | on | creditCard_1
+CREDIT_CARD_NUMBER | creditCard | Invalid card # |  | creditCard_1
+CREDIT_CARD_NAME_FULL | cardholderName | Cardholder's name |  | creditCard_1
+CREDIT_CARD_EXP_MONTH | expireMonth | Expiration Date |  | creditCard_1
+CREDIT_CARD_EXP_4_DIGIT_YEAR | expireYear | Expiration Date |  | creditCard_1
+CREDIT_CARD_VERIFICATION_CODE | securityNumber | CVV Number 3 or 4 digit number |  | creditCard_1
+UNKNOWN_TYPE | nickname | Card's nickname e.g. My Visa, Corporate card, etc |  | nickname_2
+UNKNOWN_TYPE | useAddress | Use stored address | use-stored-address | nickname_2
+UNKNOWN_TYPE | stored-address |  | ? | nickname_2
+UNKNOWN_TYPE | useAddress | Add new address | add-new-address | nickname_2
+UNKNOWN_TYPE | shouldSave | Save credit card info | on | nickname_2