[DONT COMMIT] Worklet: Implement "addModule()" algorithm for main thread worklets

third_party/WebKit/Source/core/workers/MainThreadWorklet.h

Index: third_party/WebKit/Source/core/workers/MainThreadWorklet.h
diff --git a/third_party/WebKit/Source/core/workers/MainThreadWorklet.h b/third_party/WebKit/Source/core/workers/MainThreadWorklet.h
index de5853b093bb05442a58c6c296fec91e41c83e93..15a501541c951f19b05f16e411b9cf1be41f6591 100644
--- a/third_party/WebKit/Source/core/workers/MainThreadWorklet.h
+++ b/third_party/WebKit/Source/core/workers/MainThreadWorklet.h
@@ -14,6 +14,7 @@
 namespace blink {
 
 class LocalFrame;
+class WorkletGlobalScopeProxy;
 
 // A MainThreadWorklet is a worklet that runs only on the main thread.
 // TODO(nhiroki): This is a temporary class to support module loading for main
@@ -36,6 +37,15 @@ class CORE_EXPORT MainThreadWorklet : public Worklet {
 
  protected:
   explicit MainThreadWorklet(LocalFrame*);
+
+  // Instantiates WorkletGlobalScope and adds it into |global_scope_proxies_| if
+  // there are no global scopes or additional global scopes are necessary.
+  virtual void MayAddWorkletGlobalScopes() = 0;
+
+  // "A Worklet has a list of the worklet's WorkletGlobalScopes. Initially this
+  // list is empty; it is populated when the user agent chooses to create its
+  // WorkletGlobalScope."
+  WTF::HashSet<std::unique_ptr<WorkletGlobalScopeProxy>> global_scope_proxies_;
 };
 
 }  // namespace blink