Revert "Remove FX_Alloc() null checks now that it can't return NULL."

core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.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_parser.h"
 #include "../../../include/fpdfapi/fpdf_module.h"
 #include "../../../include/fxcodec/fx_codec.h"
 #include <limits.h>
@@ skipping 22 matching lines @@
     if (pos == 0) {
         return 0;
     }
     if (zcount > UINT_MAX / 4) {
         return (FX_DWORD) - 1;
     }
     if (zcount * 4 > UINT_MAX - (pos - zcount)) {
         return (FX_DWORD) - 1;
     }
     dest_buf = FX_Alloc(FX_BYTE, zcount * 4 + (pos - zcount));
+    if (dest_buf == NULL) {
+        return (FX_DWORD) - 1;
+    }
     int state = 0;
     FX_UINT32 res = 0;
     pos = dest_size = 0;
     while (pos < src_size) {
         FX_BYTE ch = src_buf[pos++];
         if (ch == '\n' || ch == '\r' || ch == ' ' || ch == '\t') {
             continue;
         }
         if (ch == 'z') {
             FXSYS_memset32(dest_buf + dest_size, 0, 4);
@@ skipping 90 matching lines @@
             }
             i += 2;
         } else {
             break;
         }
     }
     if (dest_size >= _STREAM_MAX_SIZE_) {
         return -1;
     }
     dest_buf = FX_Alloc( FX_BYTE, dest_size);
+    if (!dest_buf) {
+        return -1;
+    }
     i = 0;
     int dest_count = 0;
     while (i < src_size) {
         if (src_buf[i] < 128) {
             FX_DWORD copy_len = src_buf[i] + 1;
             FX_DWORD buf_left = src_size - i - 1;
             if (buf_left < copy_len) {
                 FX_DWORD delta = copy_len - buf_left;
                 copy_len = buf_left;
                 FXSYS_memset8(dest_buf + dest_count + copy_len, '\0', delta);
@@ skipping 358 matching lines @@
     }
 }
 FX_DWORD FlateDecode(const FX_BYTE* src_buf, FX_DWORD src_size, FX_LPBYTE& dest_buf, FX_DWORD& dest_size)
 {
     CCodec_ModuleMgr* pEncoders = CPDF_ModuleMgr::Get()->GetCodecModule();
     if (pEncoders) {
         return pEncoders->GetFlateModule()->FlateOrLZWDecode(FALSE, src_buf, src_size, FALSE, 0, 0, 0, 0, 0, dest_buf, dest_size);
     }
     return 0;
 }