Make code compile with clang_use_chrome_plugin (part VI)

This change mainly contains files in xfa/fwl 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/2070583003

1 files changed, 4 insertions, 0 deletions

diff --git a/xfa/fwl/core/fwl_appimp.cpp b/xfa/fwl/core/fwl_appimp.cpp
index 089a6d3693..2c4258ce74 100644
--- a/xfa/fwl/core/fwl_appimp.cpp
+++ b/xfa/fwl/core/fwl_appimp.cpp
@@ -18,6 +18,10 @@ IFWL_App* IFWL_App::Create(CXFA_FFApp* pAdapter) {
   return pApp;
 }
 
+IFWL_App::IFWL_App() {}
+
+IFWL_App::~IFWL_App() {}
+
 void IFWL_App::Release() {}
 
 FWL_Error IFWL_App::Initialize() {