Add DiscardableMemoryAllocator to work around FD limit issue.

base/memory/discardable_memory_android.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/discardable_memory_android.h"
 
 #include <sys/mman.h>
 #include <unistd.h>
 
 #include "base/basictypes.h"
@@ skipping 15 matching lines @@
 // Total number of discardable memory in the process.
 int g_num_discardable_memory = 0;
 
 // Upper limit on the number of discardable memory to avoid hitting file
 // descriptor limit.
 const int kDiscardableMemoryNumLimit = 128;
 
 class DiscardableMemoryAndroid : public DiscardableMemory {
  public:
   DiscardableMemoryAndroid(int fd, void* address, size_t size)
-      : fd_(fd),
+      : DiscardableMemory(size),
+        fd_(fd),
         memory_(address),
         size_(size) {
     DCHECK_GE(fd_, 0);
     DCHECK(memory_);
   }
 
   virtual ~DiscardableMemoryAndroid() {
     internal::DeleteAshmemRegion(fd_, size_, memory_);
   }
 
@@ skipping 114 matching lines @@
     DLOG(ERROR) << "Failed to unpin memory.";
 #if !defined(NDEBUG)
   // This allows us to catch accesses to unlocked memory.
   DCHECK_EQ(0, mprotect(address, size, PROT_NONE));
 #endif
   return !failed;
 }
 
 }  // namespace internal
 }  // namespace base