Move and rename TaskTimeTracker to public interface exposed to WebThread, use in WebPerf Agent.

third_party/WebKit/Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'ContentDecryptionModuleResult.h',
@@ skipping 913 matching lines @@
       'plugins/PluginListBuilder.cpp',
       'plugins/PluginListBuilder.h',
       'scheduler/CancellableTaskFactory.cpp',
       'scheduler/CancellableTaskFactory.h',
       'scheduler/base/cancelable_closure_holder.cc',
       'scheduler/base/cancelable_closure_holder.h',
       'scheduler/base/enqueue_order.cc',
       'scheduler/base/enqueue_order.h',
       'scheduler/base/lazy_now.cc',
       'scheduler/base/lazy_now.h',
-      'scheduler/base/long_task_tracker.cc',
-      'scheduler/base/long_task_tracker.h',
       'scheduler/base/pollable_thread_safe_flag.cc',
       'scheduler/base/pollable_thread_safe_flag.h',
       'scheduler/base/queueing_time_estimator.cc',
       'scheduler/base/queueing_time_estimator.h',
       'scheduler/base/real_time_domain.cc',
       'scheduler/base/real_time_domain.h',
       'scheduler/base/task_queue_impl.cc',
       'scheduler/base/task_queue_impl.h',
       'scheduler/base/task_queue_manager.cc',
       'scheduler/base/task_queue_manager.h',
@@ skipping 353 matching lines @@
       'inspector_protocol/ParserTest.cpp',
       'mac/VersionUtilMacTest.mm',
       'mojo/KURLSecurityOriginTest.cpp',
       'network/EncodedFormDataTest.cpp',
       'network/HTTPParsersTest.cpp',
       'network/LinkHeaderTest.cpp',
       'network/NetworkUtilsTest.cpp',
       'network/ResourceRequestTest.cpp',
       'network/ResourceResponseTest.cpp',
       'scheduler/CancellableTaskFactoryTest.cpp',
-      'scheduler/base/long_task_tracker_unittest.cc',
       'scheduler/base/task_queue_manager_delegate_for_test.cc',
       'scheduler/base/task_queue_manager_unittest.cc',
       'scheduler/base/task_queue_selector_unittest.cc',
       'scheduler/base/test_count_uses_time_source.cc',
       'scheduler/base/test_time_source.cc',
       'scheduler/base/time_domain_unittest.cc',
       'scheduler/base/work_queue_sets_unittest.cc',
       'scheduler/base/queueing_time_estimator_unittest.cc',
       'scheduler/child/idle_helper_unittest.cc',
       'scheduler/child/scheduler_helper_unittest.cc',
@@ skipping 123 matching lines @@
       ['use_default_render_theme==1',
         {
           'platform_test_files': [
             'scroll/ScrollbarThemeAuraTest.cpp',
           ],
         }
       ],
     ],
   },
 }