Add tests for UserGestureIndicator class.

third_party/WebKit/Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'Clock.cpp',
@@ skipping 995 matching lines @@
       'LayoutUnitTest.cpp',
       'LifecycleContextTest.cpp',
       'PODArenaTest.cpp',
       'PODFreeListArenaTest.cpp',
       'PODIntervalTreeTest.cpp',
       'PODRedBlackTreeTest.cpp',
       'PurgeableVectorTest.cpp',
       'SharedBufferTest.cpp',
       'TimerTest.cpp',
       'TracedValueTest.cpp',
+      'UserGestureIndicatorTest.cpp',
       'UUIDTest.cpp',
       'WebScreenInfoTest.cpp',
       'WebVectorTest.cpp',
       'animation/TimingFunctionTest.cpp',
       'animation/UnitBezierTest.cpp',
       'blob/BlobDataTest.cpp',
       'clipboard/ClipboardUtilitiesTest.cpp',
       'fonts/CharacterTest.cpp',
       'fonts/FontCacheTest.cpp',
       'fonts/FontDescriptionTest.cpp',
@@ skipping 125 matching lines @@
       ['OS!="mac"',
         {
           'platform_test_files': [
             'scroll/ScrollAnimatorTest.cpp',
           ],
         }
       ],
     ],
   },
 }