Make Android gyp flags more like Linux gyp flags. Fix cases of -Wconversion-null.

runtime/vm/unit_test.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/unit_test.h"
 
 #include <stdio.h>
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
@@ skipping 128 matching lines @@
 static Dart_Handle LibraryTagHandler(Dart_LibraryTag tag,
                                      Dart_Handle library,
                                      Dart_Handle url) {
   if (tag == Dart_kScriptTag) {
     // Reload request.
     ASSERT(script_reload_key != kUnsetThreadLocalKey);
     const char* script_source =
        reinterpret_cast<const char*>(
            OSThread::GetThreadLocal(script_reload_key));
     ASSERT(script_source != NULL);
-    OSThread::SetThreadLocal(script_reload_key, NULL);
+    OSThread::SetThreadLocal(script_reload_key, 0);
     return Dart_LoadScript(url,
                            NewString(script_source),
                            0,
                            0);
   }
   if (!Dart_IsLibrary(library)) {
     return Dart_NewApiError("not a library");
   }
   if (!Dart_IsString(url)) {
     return Dart_NewApiError("url is not a string");
@@ skipping 301 matching lines @@
   }
   // Copy the remainder of in to out.
   while (*in != '\0') {
     *out++ = *in++;
   }
   *out = '\0';
 }
 
 
 }  // namespace dart