Add support for building the Dart VM for Android OS.

runtime/vm/virtual_memory_android.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/virtual_memory.h"
 
 #include <sys/mman.h>
-#include <sys/unistd.h>
 #include <unistd.h>
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 
 namespace dart {
 
 // standard MAP_FAILED causes "error: use of old-style cast" as it
 // defines MAP_FAILED as ((void *) -1)
 #undef MAP_FAILED
 #define MAP_FAILED reinterpret_cast<void*>(-1)
 
 uword VirtualMemory::page_size_ = 0;
 
 
 void VirtualMemory::InitOnce() {
   page_size_ = getpagesize();
 }
 
 
 VirtualMemory* VirtualMemory::Reserve(intptr_t size) {
+  // TODO(4480): use ashmem instead of anonymous memory

[Emily Fortuna, 2012/08/08 01:28:37]

Generally the TODO messages contain a person's ldap, like
// TODO(jackpal): Use ashmem instead of anonymous memory.
(what's 4480? It's not dartbug.com/4480 -- I saw Charlie asked you to add this,
so disregard if this is the VM-team way of doing things and this makes sense to
them.)

[cshapiro, 2012/08/08 02:57:42]

I think this is just a simple transposition error.  The value in the TODO should
be 4408 not 4480.  You might already know this but we used this convention when
we moved from the internal repository to the public repository.

[jackpal, 2012/08/08 23:06:45]

Done.

   void* address = mmap(NULL, size, PROT_NONE,
                        MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
                        -1, 0);
   if (address == MAP_FAILED) {
     return NULL;
   }
   MemoryRegion region(address, size);
   return new VirtualMemory(region, NULL);
 }
 
@@ skipping 49 matching lines @@
       prot = PROT_READ | PROT_EXEC;
       break;
     case kReadWriteExecute:
       prot = PROT_READ | PROT_WRITE | PROT_EXEC;
       break;
   }
   return (mprotect(address(), size(), prot) == 0);
 }
 
 }  // namespace dart