Deprecate MouseEvent.elementTo and elementFrom since they have the same

tools/dom/docs/docs.json

Index: tools/dom/docs/docs.json
diff --git a/tools/dom/docs/docs.json b/tools/dom/docs/docs.json
index 04839df7cd86af809987cc86ad855f02d42c8896..828992e84dcd7b31426a2d23166a815b4dc836f4 100644
--- a/tools/dom/docs/docs.json
+++ b/tools/dom/docs/docs.json
@@ -2411,6 +2411,28 @@
         ]
       }
     },
+    "MouseEvent": {
+      "members": {
+        "fromElement": [
+          "/**",
+          "   * The nonstandard way to access the element that the mouse comes",
+          "   * from in the case of a `mouseover` event.",
+          "   *",
+          "   * This member is deprecated and not cross-browser compatible; use",
+          "   * relatedTarget to get the same information in the standard way.",
+          "   */"
+        ],
+        "toElement": [
+          "/**",
+          "   * The nonstandard way to access the element that the mouse goes",
+          "   * to in the case of a `mouseout` event.",
+          "   *",
+          "   * This member is deprecated and not cross-browser compatible; use",
+          "   * relatedTarget to get the same information in the standard way.",
+          "   */"
+        ]
+      }
+    },
     "Node": {
       "members": {
         "appendChild": [