Move LayoutTestSupport.cpp/.h to Source/platform/

Source/core/core.gypi

 {
     'variables': {
         'core_idl_files': [
             'css/CSS.idl',
             'css/CSSCharsetRule.idl',
             'css/CSSFontFaceLoadEvent.idl',
             'css/CSSFontFaceRule.idl',
             'css/CSSHostRule.idl',
             'css/CSSImportRule.idl',
             'css/CSSKeyframeRule.idl',
@@ skipping 2594 matching lines @@
             'platform/CrossThreadCopier.h',
             'platform/Cursor.cpp',
             'platform/DragData.cpp',
             'platform/DragImage.cpp',
             'platform/EventTracer.cpp',
             'platform/FileMetadata.h',
             'platform/FloatConversion.h',
             'platform/HashTools.h',
             'platform/KillRing.h',
             'platform/KillRingNone.cpp',
-            'platform/LayoutTestSupport.cpp',
-            'platform/LayoutTestSupport.h',
             'platform/Length.cpp',
             'platform/LengthBox.cpp',
             'platform/LifecycleContext.cpp',
             'platform/LifecycleContext.h',
             'platform/LifecycleNotifier.cpp',
             'platform/LifecycleNotifier.h',
             'platform/LifecycleObserver.cpp',
             'platform/LifecycleObserver.h',
             'platform/MIMETypeFromURL.cpp',
             'platform/MIMETypeFromURL.h',
@@ skipping 1231 matching lines @@
                 'bison_exe': 'bison',
                 # We specify a preprocess so it happens locally and won't get
                 # distributed to goma.
                 # FIXME: /usr/bin/gcc won't exist on OSX forever. We want to
                 # use /usr/bin/clang once we require Xcode 4.x.
                 'preprocessor': '--preprocessor "/usr/bin/gcc -E -P -x c++"'
               }],
          ],
     }
 }