Separate WebIDBKey type into separate header

public/platform/WebIDBKeyType.h

Index: public/platform/WebIDBKeyType.h
diff --git a/Source/core/html/canvas/EXTFragDepth.idl b/public/platform/WebIDBKeyType.h
similarity index 81%
copy from Source/core/html/canvas/EXTFragDepth.idl
copy to public/platform/WebIDBKeyType.h
index 52a6f932c30eb3d04b60fc0e9ae33e996ea9de04..41b36832186f5759d2f3f9f0a7a9e807763a3f48 100644
--- a/Source/core/html/canvas/EXTFragDepth.idl
+++ b/public/platform/WebIDBKeyType.h
@@ -23,7 +23,21 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-[
-    NoInterfaceObject
-] interface EXTFragDepth {
+#ifndef WebIDBKeyType_h
+#define WebIDBKeyType_h
+
+namespace WebKit {
+
+enum WebIDBKeyType {
+    WebIDBKeyTypeInvalid = 0,
+    WebIDBKeyTypeArray,
+    WebIDBKeyTypeString,
+    WebIDBKeyTypeDate,
+    WebIDBKeyTypeNumber,
+    WebIDBKeyTypeNull,
+    WebIDBKeyTypeMin,
 };
+
+} // namespace WebKit
+
+#endif // WebIDBKeyType_h