Fix a bunch of -Wunused-but-set-variable warnings.

core/src/fpdfapi/fpdf_edit/fpdf_edit_image.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 "../../../include/fpdfapi/fpdf_module.h"
 #include "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../include/fxcodec/fx_codec.h"
 #include "../../../include/fpdfapi/fpdf_render.h"
@@ skipping 179 matching lines @@
         pDict->SetAtInteger(FX_BSTRC("BitsPerComponent"), 8);
         if ((iCompress & 0x03) == PDF_IMAGE_NO_COMPRESS) {
             dest_pitch = BitmapWidth * 3;
             opType = 2;
         } else {
             opType = 0;
         }
     }
     const CFX_DIBitmap* pMaskBitmap = NULL;
     if (pBitmap->HasAlpha()) {
         pMaskBitmap = pBitmap->GetAlphaMask();

[Tom Sepez, 2015/04/17 16:20:16]

// Despite it's name, GetAlphaMask() does the |new CFX_DIBitmap|.
pDeleteMaskBitmap = TRUE;

[Lei Zhang, 2015/05/08 05:40:38]

I'm punting on this file as well for now. Will revisit.

     }
     if (!pMaskBitmap && pMask) {
         FXDIB_Format maskFormat = pMask->GetFormat();
         if (maskFormat == FXDIB_1bppMask || maskFormat == FXDIB_8bppMask) {
             pMaskBitmap = pMask;

[Tom Sepez, 2015/04/17 16:20:16]

// presumably this is the non-allocating path.

         }
     }
     if (pMaskBitmap) {
         FX_INT32 maskWidth = pMaskBitmap->GetWidth();
         FX_INT32 maskHeight = pMaskBitmap->GetHeight();
         FX_LPBYTE mask_buf = NULL;
         FX_STRSIZE mask_size;
-        FX_BOOL bDeleteMask = TRUE;
         CPDF_Dictionary* pMaskDict = new CPDF_Dictionary;
         pMaskDict->SetAtName(FX_BSTRC("Type"), FX_BSTRC("XObject"));
         pMaskDict->SetAtName(FX_BSTRC("Subtype"), FX_BSTRC("Image"));
         pMaskDict->SetAtInteger(FX_BSTRC("Width"), maskWidth);
         pMaskDict->SetAtInteger(FX_BSTRC("Height"), maskHeight);
         pMaskDict->SetAtName(FX_BSTRC("ColorSpace"), FX_BSTRC("DeviceGray"));
         pMaskDict->SetAtInteger(FX_BSTRC("BitsPerComponent"), 8);
         if (pMaskBitmap->GetBPP() == 8 && (iCompress & PDF_IMAGE_MASK_LOSSY_COMPRESS) != 0) {
             _DCTEncodeBitmap(pMaskDict, pMaskBitmap, pParam ? pParam->nQuality : 75, mask_buf, mask_size);
         } else if (pMaskBitmap->GetFormat() == FXDIB_1bppMask) {
@@ skipping 12 matching lines @@
                 int a, r, g, b;
                 ArgbDecode(*(pParam->pMatteColor), a, r, g, b);
                 CPDF_Array* pMatte = new CPDF_Array;
                 pMatte->AddInteger(r);
                 pMatte->AddInteger(g);
                 pMatte->AddInteger(b);
                 pMaskDict->SetAt(FX_BSTRC("Matte"), pMatte);
             }
             pMaskStream = new CPDF_Stream(mask_buf, mask_size, pMaskDict);
             m_pDocument->AddIndirectObject(pMaskStream);
-            bDeleteMask = FALSE;
             pDict->SetAtReference(FX_BSTRC("SMask"), m_pDocument, pMaskStream);
         }
         if (pBitmap->HasAlpha()) {

[Tom Sepez, 2015/04/17 16:20:16]

This duplicates the test that lead to the allocation above, and feels fragile. 
I'd do the following:
1. rename bDeleteMask to bDeleteMaskBitmap since there are other mask_* locals
here.
2. Declare and set bDeleteMask to FALSE at line 198 at the same time we declare
pMaskBitmap.
3. set pMaskBitmap to TRUE at line 200
4. test pDeleteMaskBitmap here instead of the hasalpha.

             delete pMaskBitmap;
         }
     }
     FX_BOOL bStream = pFileWrite != NULL && pFileRead != NULL;
     if (opType == 0) {
         if (iCompress & PDF_IMAGE_LOSSLESS_COMPRESS) {
             if (pBitmap->GetBPP() == 1) {
                 _JBIG2EncodeBitmap(pDict, pBitmap, m_pDocument, dest_buf, dest_size, TRUE);
             }
         } else {
@@ skipping 105 matching lines @@
     m_Width = BitmapWidth;
     m_Height = BitmapHeight;
     if (dest_buf) {
         FX_Free(dest_buf);
     }
 }
 void CPDF_Image::ResetCache(CPDF_Page* pPage, const CFX_DIBitmap* pBitmap)
 {
     pPage->GetRenderCache()->ResetBitmap(m_pStream, pBitmap);
 }