Turn on enforce-in-pdf Clang plugin flag.

pdf/pdfium/pdfium_range.cc

Index: pdf/pdfium/pdfium_range.cc
diff --git a/pdf/pdfium/pdfium_range.cc b/pdf/pdfium/pdfium_range.cc
index 3b8371f7f6ce3b2127e94231d52fade6d2a022b3..398002959b8263e202f20caa0d8f3346a439b9ba 100644
--- a/pdf/pdfium/pdfium_range.cc
+++ b/pdf/pdfium/pdfium_range.cc
@@ -17,8 +17,9 @@ PDFiumRange::PDFiumRange(PDFiumPage* page, int char_index, int char_count)
       cached_screen_rects_zoom_(0) {
 }
 
-PDFiumRange::~PDFiumRange() {
-}
+PDFiumRange::PDFiumRange(const PDFiumRange& that) = default;
+
+PDFiumRange::~PDFiumRange() = default;
 
 void PDFiumRange::SetCharCount(int char_count) {
   char_count_ = char_count;