Add functionality for copying text within form text fields and form combobox text fields

pdf/pdfium/pdfium_page.h

Index: pdf/pdfium/pdfium_page.h
diff --git a/pdf/pdfium/pdfium_page.h b/pdf/pdfium/pdfium_page.h
index acb2e7df3ab76422b05198a5d001c32a4cc277a4..1663e2083dab45a83b76668defb0326f4e1daed9 100644
--- a/pdf/pdfium/pdfium_page.h
+++ b/pdf/pdfium/pdfium_page.h
@@ -51,9 +51,11 @@ class PDFiumPage {
 
   enum Area {
     NONSELECTABLE_AREA,
-    TEXT_AREA,
-    WEBLINK_AREA,  // Area is a hyperlink.
-    DOCLINK_AREA,  // Area is a link to a different part of the same document.
+    TEXT_AREA,       // Area contains regular, selectable text not within form
+                     // fields.
+    WEBLINK_AREA,    // Area is a hyperlink.
+    DOCLINK_AREA,    // Area is a link to a different part of the same document.
+    FORM_TEXT_AREA,  // Area is a form field text field.
   };
 
   struct LinkTarget {