Expose WorkerPool to blink

third_party/WebKit/Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
+      'BackgroundTask.cpp',
+      'BackgroundTask.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'Clock.cpp',
       'Clock.h',
       'ContentDecryptionModuleResult.h',
       'ContentSettingCallbacks.cpp',
       'ContentSettingCallbacks.h',
       'ContentType.cpp',
       'ContentType.h',
       'ContextMenu.cpp',
@@ skipping 1032 matching lines @@
       'weborigin/KURLTest.cpp',
       'weborigin/OriginAccessEntryTest.cpp',
       'weborigin/SchemeRegistryTest.cpp',
       'weborigin/SecurityOriginTest.cpp',
       'weborigin/SecurityPolicyTest.cpp',
     ],
     # NOTE: These are legacy unit tests and tests that require a Platform
     # object. Do not add more unless the test requires a Platform object.
     # These tests are a part of the web:webkit_unit_tests binary.
     'platform_web_unittest_files': [
+      'BackgroundTaskTest.cpp',
       'fonts/FontPlatformDataTest.cpp',
       'fonts/TestFontSelector.h',
       'graphics/BitmapImageTest.cpp',
       'graphics/Canvas2DLayerBridgeTest.cpp',
       'graphics/DeferredImageDecoderTest.cpp',
       'graphics/GraphicsLayerTest.cpp',
       'graphics/ImageDecodingStoreTest.cpp',
       'graphics/ImageFrameGeneratorTest.cpp',
       'graphics/ImageLayerChromiumTest.cpp',
       'graphics/test/MockImageDecoder.h',
@@ skipping 48 matching lines @@
       ['OS!="mac"',
         {
           'platform_test_files': [
             'scroll/ScrollAnimatorTest.cpp',
           ],
         }
       ],
     ],
   },
 }