React immediately to memory pressure on foreground threads

test/unittests/unittests.gyp

 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # The sources are kept automatically in sync with BUILD.gn.
 
 {
   'variables': {
     'v8_code': 1,
     'unittests_sources': [  ### gcmole(all) ###
+      'api/isolate-unittest.cc',
       'base/atomic-utils-unittest.cc',
       'base/bits-unittest.cc',
       'base/cpu-unittest.cc',
       'base/division-by-constant-unittest.cc',
       'base/flags-unittest.cc',
       'base/functional-unittest.cc',
       'base/ieee754-unittest.cc',
       'base/logging-unittest.cc',
       'base/iterator-unittest.cc',
       'base/platform/condition-variable-unittest.cc',
@@ skipping 256 matching lines @@
             '../../gypfiles/isolate.gypi',
           ],
           'sources': [
             'unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }