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

core/src/fxcrt/fx_basic_bstring.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 <stddef.h>  // For offsetof().
 
 #include "../../include/fxcrt/fx_basic.h"
 #include "../../../third_party/base/numerics/safe_math.h"
@@ skipping 55 matching lines @@
     // Now round to an 8-byte boundary. We'd expect that this is the minimum
     // granularity of any of the underlying allocators, so there may be cases
     // where we can save a re-alloc when adding a few characters to a string
     // by using this otherwise wasted space.
     nSize += 7;
     int totalSize = nSize.ValueOrDie() & ~7;
     int usableSize = totalSize - overhead;
     FXSYS_assert(usableSize >= nLen);
 
     void* pData = FX_Alloc(FX_BYTE, totalSize);
+    if (!pData) {
+        return NULL;
+    }
     return new (pData) StringData(nLen, usableSize);
 }
 CFX_ByteString::~CFX_ByteString()
 {
     if (m_pData) {
         m_pData->Release();
     }
 }
 CFX_ByteString::CFX_ByteString(FX_LPCSTR lpsz, FX_STRSIZE nLen)
 {
@@ skipping 1038 matching lines @@
         scale /= 10;
     }
     return buf_size;
 }
 CFX_ByteString CFX_ByteString::FormatFloat(FX_FLOAT d, int precision)
 {
     FX_CHAR buf[32];
     FX_STRSIZE len = FX_ftoa(d, buf);
     return CFX_ByteString(buf, len);
 }