Devtools: Use Event.deepPath as a function if available.

third_party/WebKit/Source/devtools/front_end/devtools.js

Index: third_party/WebKit/Source/devtools/front_end/devtools.js
diff --git a/third_party/WebKit/Source/devtools/front_end/devtools.js b/third_party/WebKit/Source/devtools/front_end/devtools.js
index 05c2b25a3800a9cd76bba88af007f8f8a9264b7d..d486dc79f534dd40712a1a27ae385492f5a6a3c9 100644
--- a/third_party/WebKit/Source/devtools/front_end/devtools.js
+++ b/third_party/WebKit/Source/devtools/front_end/devtools.js
@@ -961,3 +961,7 @@ if (!DOMTokenList.prototype.__originalDOMTokenListToggle) {
         return this.__originalDOMTokenListToggle(token, !!force);
     }
 }
+
+// Support for legacy (<M49) frontends. Remove in M52.
+if (Object.getOwnPropertyDescriptor(Event.prototype, "deepPath"))

[dgozman, 2016/02/02 02:45:45]

Please move this code (and a block above while we are here) into
installBackwardsCompatibility method.

[samli, 2016/02/03 00:07:11]

Done.

+    Event.prototype.deepPath = undefined;