Fixed WebDragData's wrong dependency.

Source/web/web.gypi

 {
   'variables': {
     'web_files': [
       'AssertMatchingEnums.cpp',
       'AssociatedURLLoader.cpp',
       'AssociatedURLLoader.h',
       'ChromeClientImpl.cpp',
       'ChromeClientImpl.h',
       'ColorChooserPopupUIController.cpp',
       'ColorChooserPopupUIController.h',
@@ skipping 122 matching lines @@
       'WebDataSourceImpl.cpp',
       'WebDataSourceImpl.h',
       'WebDatabase.cpp',
       'WebDateTimeSuggestion.cpp',
       'WebDevToolsAgentImpl.cpp',
       'WebDevToolsAgentImpl.h',
       'WebDevToolsFrontendImpl.cpp',
       'WebDevToolsFrontendImpl.h',
       'WebDocument.cpp',
       'WebDocumentType.cpp',
-      'WebDragData.cpp',
       'WebElement.cpp',
       'WebElementCollection.cpp',
       'WebEmbeddedWorkerImpl.cpp',
       'WebEmbeddedWorkerImpl.h',
       'WebEncryptedMediaRequest.cpp',
       'WebEntities.cpp',
       'WebEntities.h',
       'WebFileChooserCompletionImpl.cpp',
       'WebFileChooserCompletionImpl.h',
       'WebFontDescription.cpp',
@@ skipping 199 matching lines @@
       ['os_posix==1 and OS!="mac"',
         {
           'web_unittest_files': [
             'tests/LocaleICUTest.cpp',
           ],
         }
       ],
     ],
   },
 }