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, 2 deletions

diff --git a/xfa/fwl/basewidget/ifwl_tooltip.h b/xfa/fwl/basewidget/ifwl_tooltip.h
index 5b8dff1b3b..db048d3ff6 100644
--- a/xfa/fwl/basewidget/ifwl_tooltip.h
+++ b/xfa/fwl/basewidget/ifwl_tooltip.h
@@ -21,8 +21,10 @@ class IFWL_ToolTip;
 
 class IFWL_ToolTipDP : public IFWL_DataProvider {
  public:
-  virtual FWL_Error GetCaption(IFWL_Widget* pWidget,
-                               CFX_WideString& wsCaption) = 0;
+  // IFWL_DataProvider
+  FWL_Error GetCaption(IFWL_Widget* pWidget,
+                       CFX_WideString& wsCaption) override = 0;
+
   virtual int32_t GetInitialDelay(IFWL_Widget* pWidget) = 0;
   virtual int32_t GetAutoPopDelay(IFWL_Widget* pWidget) = 0;
   virtual CFX_DIBitmap* GetToolTipIcon(IFWL_Widget* pWidget) = 0;