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

pdf/pdfium/pdfium_page.cc

Index: pdf/pdfium/pdfium_page.cc
diff --git a/pdf/pdfium/pdfium_page.cc b/pdf/pdfium/pdfium_page.cc
index 7d85d36aa315e5447995c168c4e4a86caf7a9d5d..b9ec998da4c03e632271efbfbec0c3e84ac71f4f 100644
--- a/pdf/pdfium/pdfium_page.cc
+++ b/pdf/pdfium/pdfium_page.cc
@@ -283,6 +283,10 @@ PDFiumPage::Area PDFiumPage::GetCharIndex(const pp::Point& point,
       return area;
   } else if (control > FPDF_FORMFIELD_UNKNOWN) {
     *form_type = control;
+
+    if (*form_type == FPDF_FORMFIELD_TEXTFIELD) {
+      return PDFiumPage::FORM_TEXT_AREA;
+    }
     return PDFiumPage::NONSELECTABLE_AREA;
   }