Clear navigation_handle early in RenderFrameHostImpl destructor.

content/browser/frame_host/render_frame_host_impl.cc

Index: content/browser/frame_host/render_frame_host_impl.cc
diff --git a/content/browser/frame_host/render_frame_host_impl.cc b/content/browser/frame_host/render_frame_host_impl.cc
index 34c8572c4391e87f2198abd6d78498ecbe4be1c4..4fa864f1751c162ff9a630d85dc6409b0f36d21f 100644
--- a/content/browser/frame_host/render_frame_host_impl.cc
+++ b/content/browser/frame_host/render_frame_host_impl.cc
@@ -383,6 +383,10 @@ RenderFrameHostImpl::RenderFrameHostImpl(SiteInstance* site_instance,
 }
 
 RenderFrameHostImpl::~RenderFrameHostImpl() {
+  // Destroying navigation handle may call into delegates/observers,
+  // so we do it early while |this| object is still in a sane state.
+  navigation_handle_.reset();
+
   // Release the WebUI instances before all else as the WebUI may accesses the
   // RenderFrameHost during cleanup.
   ClearAllWebUI();