Make code compile with clang_use_chrome_plugin (part I)

This change contains files in core/fpdfapi directory. This is part
of the efforts to make PDFium code compilable by Clang chromium
style plugins.

The changes are mainly the following:
-- move inline constructor/destructor of complex class/struct out-of-line;
-- add constructor/destructor of complex class/struct if not
   explicitly defined;
-- add explicit out-of-line copy constructor when needed;
-- move inline virtual functions out-of-line;
-- Properly mark virtual functions with 'override';
-- some minor cleanups;

BUG=pdfium:469

Review-Url: https://codereview.chromium.org/2060973002

1 files changed, 1 insertions, 1 deletions

diff --git a/core/fpdfapi/fpdf_page/include/cpdf_page.h b/core/fpdfapi/fpdf_page/include/cpdf_page.h
index 99734889af..e73c41db79 100644
--- a/core/fpdfapi/fpdf_page/include/cpdf_page.h
+++ b/core/fpdfapi/fpdf_page/include/cpdf_page.h
@@ -26,7 +26,7 @@ class CPDF_Page : public CPDF_PageObjectHolder {
   CPDF_Page(CPDF_Document* pDocument,
             CPDF_Dictionary* pPageDict,
             bool bPageCache);
-  ~CPDF_Page();
+  ~CPDF_Page() override;
 
   void ParseContent();