Make code compile with clang_use_chrome_plugin (part IV)

This change mainly contains files in fpdfsdk/ 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 plus removing an unused file and splitting
cxfa_eventparam out from fxfa.h

BUG=pdfium:469

Review-Url: https://codereview.chromium.org/2062313002
diff --git a/fpdfsdk/javascript/cjs_runtime.cpp b/fpdfsdk/javascript/cjs_runtime.cpp
index 020472e..2bcdc22 100644
--- a/fpdfsdk/javascript/cjs_runtime.cpp
+++ b/fpdfsdk/javascript/cjs_runtime.cpp
@@ -210,6 +210,10 @@
   }
 }
 
+CPDFSDK_Document* CJS_Runtime::GetReaderDocument() {
+  return m_pDocument;
+}
+
 int CJS_Runtime::Execute(const CFX_WideString& script, CFX_WideString* info) {
   FXJSErr error = {};
   int nRet = FXJS_Execute(m_isolate, script, &error);