Refactor viewport initialization logic out of WebViewImpl.

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',
@@ skipping 1875 matching lines @@
             'dom/TreeScopeAdopter.h',
             'dom/TreeWalker.cpp',
             'dom/TreeWalker.h',
             'dom/UIEvent.cpp',
             'dom/UIEventWithKeyState.cpp',
             'dom/UserActionElementSet.h',
             'dom/UserActionElementSet.cpp',
             'dom/UserGestureIndicator.cpp',
             'dom/UserTypingGestureIndicator.cpp',
             'dom/ViewportArguments.cpp',
+            'dom/ViewportAttributes.cpp',
             'dom/VisitedLinkState.cpp',
             'dom/VisitedLinkState.h',
             'dom/WebCoreMemoryInstrumentation.cpp',
             'dom/WebCoreMemoryInstrumentation.h',
             'dom/WheelEvent.cpp',
             'dom/WheelEvent.h',
             'dom/WindowEventContext.cpp',
             'dom/WindowEventContext.h',
             'dom/default/PlatformMessagePortChannel.cpp',
             'dom/default/PlatformMessagePortChannel.h',
@@ skipping 1769 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++"'
               }],
          ],
     }
 }