Fix Android build warnings

runtime/vm/simulator_arm.cc

 // Copyright (c) 2013, 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 <math.h>  // for isnan.
 #include <setjmp.h>
 #include <stdlib.h>
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_ARM)
@@ skipping 690 matching lines @@
 
 bool Simulator::HasExclusiveAccessAndOpen(uword addr) {
   Isolate* isolate = Isolate::Current();
   ASSERT(isolate != NULL);
   bool result = false;
   for (int i = 0; i < kNumAddressTags; i++) {
     if (exclusive_access_state_[i].isolate == isolate) {
       if (exclusive_access_state_[i].addr == addr) {
         result = true;
       }
-      exclusive_access_state_[i].addr = NULL;
+      exclusive_access_state_[i].addr = static_cast<uword>(NULL);
       continue;
     }
     if (exclusive_access_state_[i].addr == addr) {
-      exclusive_access_state_[i].addr = NULL;
+      exclusive_access_state_[i].addr = static_cast<uword>(NULL);
     }
   }
   return result;
 }
 
 
 void Simulator::InitOnce() {
   // Setup exclusive access state.
   exclusive_access_lock_ = new Mutex();
   for (int i = 0; i < kNumAddressTags; i++) {
     exclusive_access_state_[i].isolate = NULL;
-    exclusive_access_state_[i].addr = NULL;
+    exclusive_access_state_[i].addr = static_cast<uword>(NULL);
   }
   next_address_tag_ = 0;
 }
 
 
 Simulator::Simulator() {
   // Setup simulator support first. Some of this information is needed to
   // setup the architecture state.
   // We allocate the stack here, the size is computed as the sum of
   // the size specified by the user and the buffer space needed for
@@ skipping 361 matching lines @@
   uint8_t* ptr = reinterpret_cast<uint8_t*>(addr);
   *ptr = value;
 }
 
 
 // Synchronization primitives support.
 void Simulator::ClearExclusive() {
   // This lock is initialized in Simulator::InitOnce().
   MutexLocker ml(exclusive_access_lock_);
   // Set exclusive access to open state for this isolate.
-  HasExclusiveAccessAndOpen(NULL);
+  HasExclusiveAccessAndOpen(static_cast<uword>(NULL));
 }
 
 
 intptr_t Simulator::ReadExclusiveW(uword addr, Instr* instr) {
   // This lock is initialized in Simulator::InitOnce().
   MutexLocker ml(exclusive_access_lock_);
   SetExclusiveAccess(addr);
   return ReadW(addr, instr);
 }
 
@@ skipping 2679 matching lines @@
   set_register(kExceptionObjectReg, bit_cast<int32_t>(raw_exception));
   set_register(kStackTraceObjectReg, bit_cast<int32_t>(raw_stacktrace));
   buf->Longjmp();
 }
 
 }  // namespace dart
 
 #endif  // !defined(HOST_ARCH_ARM)
 
 #endif  // defined TARGET_ARCH_ARM