Introduce the fallback theme engine that will be used to paint a fallback UI

Source/Platform/chromium/public/WebFallbackThemeEngine.h

Index: Source/Platform/chromium/public/WebFallbackThemeEngine.h
diff --git a/Source/Platform/chromium/public/default/WebThemeEngine.h b/Source/Platform/chromium/public/WebFallbackThemeEngine.h
similarity index 96%
copy from Source/Platform/chromium/public/default/WebThemeEngine.h
copy to Source/Platform/chromium/public/WebFallbackThemeEngine.h
index f84f292d7f878e30ee3498089c8d976c15e8044b..ea87a8aa0d5394a76f302f8e85f743fb18c32d5f 100644
--- a/Source/Platform/chromium/public/default/WebThemeEngine.h
+++ b/Source/Platform/chromium/public/WebFallbackThemeEngine.h
@@ -28,18 +28,18 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef WebThemeEngine_h
-#define WebThemeEngine_h
+#ifndef WebFallbackThemeEngine_h
+#define WebFallbackThemeEngine_h
 
-#include "../WebCanvas.h"
-#include "../WebColor.h"
-#include "../WebSize.h"
+#include "WebCanvas.h"
+#include "WebColor.h"
+#include "WebSize.h"
 
 namespace WebKit {
 
 struct WebRect;
 
-class WebThemeEngine {
+class WebFallbackThemeEngine {
 public:
     // The UI part which is being accessed.
     enum Part {