Convert NavigationTracingObserver to use the new navigation callbacks.

chrome/browser/tracing/navigation_tracing.h

Index: chrome/browser/tracing/navigation_tracing.h
diff --git a/chrome/browser/tracing/navigation_tracing.h b/chrome/browser/tracing/navigation_tracing.h
index f26287e5185b58fdc667612bb5cbc0f3723bbd61..709379d6f8275f131f442e5f31650324efac5d32 100644
--- a/chrome/browser/tracing/navigation_tracing.h
+++ b/chrome/browser/tracing/navigation_tracing.h
@@ -28,12 +28,11 @@ class NavigationTracingObserver
   ~NavigationTracingObserver() override;
 
   // content::WebContentsObserver implementation.
-  void DidStartProvisionalLoadForFrame(
-      content::RenderFrameHost* render_frame_host,
-      const GURL& validated_url,
-      bool is_error_page) override;
+  void DidStartNavigation(
+      content::NavigationHandle* navigation_handle) override;
 
-  static content::BackgroundTracingManager::TriggerHandle navigation_handle;
+  static content::BackgroundTracingManager::TriggerHandle
+      navigation_trigger_handle_;
 
   DISALLOW_COPY_AND_ASSIGN(NavigationTracingObserver);
 };