Revert of Remove wasm compile time option and enable wasm behind a runtime flag.

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.
 
 {
   'variables': {
     'v8_code': 1,
   },
   'includes': ['../../build/toolchain.gypi', '../../build/features.gypi'],
   'targets': [
@@ skipping 92 matching lines @@
         'heap/bitmap-unittest.cc',
         'heap/gc-idle-time-handler-unittest.cc',
         'heap/memory-reducer-unittest.cc',
         'heap/heap-unittest.cc',
         'heap/scavenge-job-unittest.cc',
         'locked-queue-unittest.cc',
         'run-all-unittests.cc',
         'runtime/runtime-interpreter-unittest.cc',
         'test-utils.h',
         'test-utils.cc',
-        'wasm/ast-decoder-unittest.cc',
-        'wasm/encoder-unittest.cc',
-        'wasm/module-decoder-unittest.cc',
-        'wasm/wasm-macro-gen-unittest.cc',
       ],
       'conditions': [
         ['v8_target_arch=="arm"', {
           'sources': [  ### gcmole(arch:arm) ###
             'compiler/arm/instruction-selector-arm-unittest.cc',
           ],
         }],
         ['v8_target_arch=="arm64"', {
           'sources': [  ### gcmole(arch:arm64) ###
             'compiler/arm64/instruction-selector-arm64-unittest.cc',
@@ skipping 39 matching lines @@
           # that show up because we use -std=gnu++0x instead of -std=c++11.
           'cflags!': [
             '-pedantic',
           ],
           'direct_dependent_settings': {
             'cflags!': [
               '-pedantic',
             ],
           },
         }],
+        ['v8_wasm!=0', {
+          'sources': [
+            'wasm/ast-decoder-unittest.cc',
+            'wasm/encoder-unittest.cc',
+            'wasm/module-decoder-unittest.cc',
+            'wasm/wasm-macro-gen-unittest.cc',
+          ],
+        }],
       ],
     },
   ],
   'conditions': [
     ['test_isolation_mode != "noop"', {
       'targets': [
         {
           'target_name': 'unittests_run',
           'type': 'none',
           'dependencies': [
             'unittests',
           ],
           'includes': [
             '../../build/isolate.gypi',
           ],
           'sources': [
             'unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }