Make down-conversion explicit from CFX_Widetring to CFX_WideStringC.

xfa/fxfa/app/xfa_ffimageedit.cpp

Index: xfa/fxfa/app/xfa_ffimageedit.cpp
diff --git a/xfa/fxfa/app/xfa_ffimageedit.cpp b/xfa/fxfa/app/xfa_ffimageedit.cpp
index ce69b1242b7bec89760269ed1af92ab877b3ee03..97c83ee17c173e8230f41aa7c62b8312b2a39070 100644
--- a/xfa/fxfa/app/xfa_ffimageedit.cpp
+++ b/xfa/fxfa/app/xfa_ffimageedit.cpp
@@ -108,7 +108,8 @@ FX_BOOL CXFA_FFImageEdit::OnLButtonDown(uint32_t dwFlags,
   CFX_WideString wsFilter;
   pAppProvider->LoadString(XFA_IDS_ImageFilter, wsFilter);
   CFX_WideStringArray wsPathArray;
-  pAppProvider->ShowFileDialog(wsTitle, wsFilter, wsPathArray);
+  pAppProvider->ShowFileDialog(wsTitle.AsWideStringC(),
+                               wsFilter.AsWideStringC(), wsPathArray);
   int32_t iSize = wsPathArray.GetSize();
   if (iSize < 1) {
     return TRUE;
@@ -125,7 +126,8 @@ FX_BOOL CXFA_FFImageEdit::OnLButtonDown(uint32_t dwFlags,
   CFX_WideString wsContentType(L"image/");
   wsContentType += wsFilePath.Right(nLen - nIndex - 1);
   wsContentType.MakeLower();
-  FXCODEC_IMAGE_TYPE eImageType = XFA_GetImageType(wsContentType);
+  FXCODEC_IMAGE_TYPE eImageType =
+      XFA_GetImageType(wsContentType.AsWideStringC());

[Lei Zhang, 2016/04/05 00:45:48]

XFA_GetImageType() takes the CFX_WideStringC and makes a CFX_WideString out of
it. Just pass in |wsContentType| by const ref instead? Ditto in
xfa/fxfa/app/xfa_ffwidget.cpp.

[Tom Sepez, 2016/04/05 16:34:22]

There are a bunch of these.  I was planning on a follow-up that looked at
routines that take strings, and asks, "does the string persist beyond the call?"
 If yes, the the routine should take a xxxString, if not, then a xxxStringC. In
the first case, the caller may already have one, and in the second case, we may
avoid making one.

[Tom Sepez, 2016/04/05 18:47:17]

Anyway, I did this here, but the first thing the XFA_ routine does is make a
copy of the string so it can lower-case it. 

   if (eImageType == FXCODEC_IMAGE_UNKNOWN) {
     return TRUE;
   }
@@ -147,7 +149,8 @@ FX_BOOL CXFA_FFImageEdit::OnLButtonDown(uint32_t dwFlags,
     m_pDataAcc->SetImageEditImage(NULL);
     pFileRead->Release();
   }
-  m_pDataAcc->SetImageEdit(wsContentType, CFX_WideStringC(), wsImage);
+  m_pDataAcc->SetImageEdit(wsContentType.AsWideStringC(), CFX_WideStringC(),
+                           wsImage.AsWideStringC());
   m_pDataAcc->LoadImageEditImage();
   AddInvalidateRect();
   m_pDocView->SetChangeMark();