Remove DOMWindow::isSecureContext.

It has no definition; all real calls access LocalDOMWindow::isSecureContext.

Change-Id: I82c37f54baef4de6f5efde7702874eaf02d0e232
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1816487
Auto-Submit: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Lucas Gadani <lfg@chromium.org>
Reviewed-by: Lucas Gadani <lfg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698501}

third_party/blink/renderer/core/frame/dom_window.h

@@ -123,8 +123,6 @@ class CORE_EXPORT DOMWindow : public EventTargetWithInlineData {
   // See https://bugs.webkit.org/show_bug.cgi?id=62054
   bool IsCurrentlyDisplayedInFrame() const;
 
-  bool isSecureContext() const;
-
   InputDeviceCapabilitiesConstants* GetInputDeviceCapabilities();
 
   void PostMessageForTesting(scoped_refptr<SerializedScriptValue> message,