Fix GCC warnings to be ready for GCC standalone build

fpdfsdk/fpdfxfa/fpdfxfa_doc.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "fpdfsdk/fpdfxfa/include/fpdfxfa_doc.h"
 
 #include "core/fpdfapi/fpdf_parser/include/cpdf_array.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_document.h"
@@ skipping 336 matching lines @@
 
   CXFA_WidgetAcc* pWidgetAcc = hWidget->GetDataAcc();
   int nRotate = 0;
 #ifdef PDF_ENABLE_XFA
   nRotate = pWidgetAcc->GetRotate();
 #endif
 
   CPDFDoc_Environment* pEnv = m_pSDKDoc->GetEnv();
   if (!pEnv)
     return FALSE;
-  FS_RECTF pageViewRect;
+  FS_RECTF pageViewRect = {0.0f, 0.0f, 0.0f, 0.0f};
   pEnv->FFI_GetPageViewRect(pPage, pageViewRect);
 
   CFX_FloatRect rcAnchor;
 
   rcAnchor.left = rtAnchor.left;
   rcAnchor.top = rtAnchor.bottom();
   rcAnchor.right = rtAnchor.right();
   rcAnchor.bottom = rtAnchor.top;
 
   int t1, t2, t;
@@ skipping 908 matching lines @@
   }
 
   return _GetHValueByName(szPropName, hValue,
                           m_pSDKDoc->GetEnv()->GetJSRuntime());
 }
 FX_BOOL CPDFXFA_Document::_GetHValueByName(const CFX_ByteStringC& utf8Name,
                                            FXJSE_HVALUE hValue,
                                            IJS_Runtime* runTime) {
   return runTime->GetHValueByName(utf8Name, hValue);
 }