Add world type accessor to DomWorld.

This will be used in upcoming instrumentation logic.

BUG=1080672

Change-Id: Ic465c9277e7c84c56183691554937f231fc6a340
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2487848
Auto-Submit: Chris Hamilton <chrisha@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819258}

third_party/blink/renderer/platform/bindings/dom_wrapper_world.h

@@ -150,6 +150,7 @@ class PLATFORM_EXPORT DOMWrapperWorld : public RefCounted<DOMWrapperWorld> {
            world_type_ == WorldType::kInspectorIsolated;
   }
 
+  WorldType GetWorldType() const { return world_type_; }
   int GetWorldId() const { return world_id_; }
   DOMDataStore& DomDataStore() const { return *dom_data_store_; }