Cover CJS_Field::ParseFieldName() from JavaScript.

Change-Id: I08f77d47a6e6ca76118aad6199d1102035b39297
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/63571
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/testing/resources/javascript/field_methods.in b/testing/resources/javascript/field_methods.in
index 918f672..81b9eed 100644
--- a/testing/resources/javascript/field_methods.in
+++ b/testing/resources/javascript/field_methods.in
@@ -10,12 +10,26 @@
 
 function testGetField() {
   try {
+    var empty =  this.getField("");
+    app.alert("empty is " + empty.name);
     var field = this.getField("MyField");
     app.alert("field is " + field.name);
     var button = this.getField("MyField.MyPushButton");
     app.alert("button is " + button.name);
     var nonesuch = this.getField("MyField.nonesuch");
     app.alert("nonesuch is " + nonesuch);
+    var dotdot = this.getField("MyField..nonesuch");
+    app.alert("dotdot is " + dotdot.name);
+    var tripledot = this.getField("MyField...nonesuch");
+    app.alert("tripledot is " + tripledot.name);
+    var quaddot = this.getField("MyField....nonesuch");
+    app.alert("quaddot is " + quaddot.name);
+    var dotdot1 = this.getField("MyField..nonesuch      ");
+    app.alert("dotdot1 is " + dotdot1.name);
+    var dotdot2 = this.getField("MyField..MyPushButton");
+    app.alert("dotdot2 is " + dotdot2.name);
+    var dotdot3 = this.getField("MyField..3");
+    app.alert("dotdot3 is " + dotdot3.name);
   } catch (e) {
     app.alert("Unexpected error: " + e);
   }
diff --git a/testing/resources/javascript/field_methods_expected.txt b/testing/resources/javascript/field_methods_expected.txt
index 285237d..8d7ec84 100644
--- a/testing/resources/javascript/field_methods_expected.txt
+++ b/testing/resources/javascript/field_methods_expected.txt
@@ -1,6 +1,13 @@
+Alert: empty is 
 Alert: field is MyField
 Alert: button is MyField.MyPushButton
 Alert: nonesuch is undefined
+Alert: dotdot is 
+Alert: tripledot is MyField..nonesuch
+Alert: quaddot is MyField..nonesuch
+Alert: dotdot1 is 
+Alert: dotdot2 is MyField.MyPushButton
+Alert: dotdot3 is MyField
 Alert: found 7 sub-fields:
 Alert: MyField.MyCheckBox
 Alert: MyField.MyFile