Cleanup: Remove WeakPtr usage in WebSharedWorkerImpl

public/web/WebSharedWorkerClient.h

Index: public/web/WebSharedWorkerClient.h
diff --git a/public/web/WebSharedWorkerClient.h b/public/web/WebSharedWorkerClient.h
index e79c1fc37961d0b111e846f9e7a6e7d74551a14a..cae31174b8212268b3e659d5768f8f952ac60088 100644
--- a/public/web/WebSharedWorkerClient.h
+++ b/public/web/WebSharedWorkerClient.h
@@ -48,6 +48,9 @@ class WebWorkerContentSettingsClientProxy;
 // Provides an interface back to the in-page script object for a worker.
 // All functions are expected to be called back on the thread that created
 // the Worker object, unless noted.
+// An instance of this class must outlive or must have the identical lifetime
+// as WebSharedWorker (i.e. must be kept alive until workerScriptLoadFailed()
+// or workerContextDestroyed() is called).
 class WebSharedWorkerClient {
 public:
     virtual void workerContextClosed() = 0;