7184238: add OnUnconfirmedTapConvertedToTap override

Upstream added OnUnconfirmedTapConvertedToTap as a pure virtual method
to RenderWidgetHostViewBase to inform root view when child frame converts
an unconfirmed tap. Add empty override for offscreen rendering.

Ref: https://chromium-review.googlesource.com/c/chromium/src/+/7184238

shell/browser/osr/osr_render_widget_host_view.h

@@ -143,6 +143,7 @@ class OffScreenRenderWidgetHostView
   void ShowWithVisibility(content::PageVisibilityState page_visibility) final;
   void Destroy() override;
   void UpdateTooltipUnderCursor(const std::u16string&) override {}
+  void OnUnconfirmedTapConvertedToTap() override {}
   input::CursorManager* GetCursorManager() override;
   void CopyFromSurface(
       const gfx::Rect& src_rect,