Issue #4826 - Use latch to replace thread-sleeping in tests

libadblockplus.gyp

 {
   'conditions': [[
     # We don't want to use curl on Windows and Android, skip the check there
     'OS=="win" or OS=="android"',
     {
       'variables': {
         'have_curl': 0
       }
     },
     {
@@ skipping 31 matching lines @@
       'src/DefaultFileSystem.cpp',
       'src/FileSystemJsObject.cpp',
       'src/FilterEngine.cpp',
       'src/GlobalJsObject.cpp',
       'src/JsContext.cpp',
       'src/JsEngine.cpp',
       'src/JsEngineInternal.h',
       'src/JsEngineTransition.h',
       'src/JsError.cpp',
       'src/JsValue.cpp',
+      'src/Latch.cpp',
+      'src/Latch.h',
       'src/Notification.cpp',
       'src/ReferrerMapping.cpp',
       'src/Scheduler.cpp',
       'src/Timeout.cpp',
       'src/Timeout.h',
       'src/Utils.cpp',
       'src/Value.h',
       'src/V8Upgrade.h',
       'src/WebRequestJsObject.cpp',
       '<(INTERMEDIATE_DIR)/adblockplus.js.cpp'
@@ skipping 113 matching lines @@
       'test/BaseJsTest.h',
       'test/BaseJsTest.cpp',
       'test/AppInfoJsObject.cpp',
       'test/ConsoleJsObject.cpp',
       'test/DefaultFileSystem.cpp',
       'test/FileSystemJsObject.cpp',
       'test/FilterEngine.cpp',
       'test/GlobalJsObject.cpp',
       'test/JsEngine.cpp',
       'test/JsValue.cpp',
+      'test/JsLatch.cpp',
+      'test/JsLatch.h',
+      'test/LatchTest.cpp',
       'test/Notification.cpp',
       'test/PausePoint.cpp',
       'test/PausePoint.h',
       'test/Prefs.cpp',
       'test/ReferrerMapping.cpp',
       'test/SchedulerTest.cpp',
       'test/TimeoutTest.cpp',
       'test/UpdateCheck.cpp',
       'test/WebRequest.cpp'
     ],
     'msvs_settings': {
       'VCLinkerTool': {
         'SubSystem': '1',   # Console
         'EntryPointSymbol': 'mainCRTStartup',
       },
     },
   }]
 }