Add a NavigationThrottle to the public content/ interface

content/test/web_contents_observer_sanity_checker.cc

Index: content/test/web_contents_observer_sanity_checker.cc
diff --git a/content/test/web_contents_observer_sanity_checker.cc b/content/test/web_contents_observer_sanity_checker.cc
index 09151e89135750a398e7a6b909227f4418abb1ed..19fabc35b578cb7666cda4e9b952e1179db7ad87 100644
--- a/content/test/web_contents_observer_sanity_checker.cc
+++ b/content/test/web_contents_observer_sanity_checker.cc
@@ -129,6 +129,7 @@ void WebContentsObserverSanityChecker::DidStartNavigation(
   CHECK(navigation_handle->GetNetErrorCode() == net::OK);
   CHECK(!navigation_handle->HasCommittedDocument());
   CHECK(!navigation_handle->HasCommittedErrorPage());
+  CHECK_EQ(navigation_handle->GetWebContents(), web_contents());
 
   ongoing_navigations_.insert(navigation_handle);
 }
@@ -141,6 +142,7 @@ void WebContentsObserverSanityChecker::DidRedirectNavigation(
   CHECK(navigation_handle->GetNetErrorCode() == net::OK);
   CHECK(!navigation_handle->HasCommittedDocument());
   CHECK(!navigation_handle->HasCommittedErrorPage());
+  CHECK_EQ(navigation_handle->GetWebContents(), web_contents());
 }
 
 void WebContentsObserverSanityChecker::DidCommitNavigation(
@@ -154,6 +156,7 @@ void WebContentsObserverSanityChecker::DidCommitNavigation(
                 navigation_handle->GetNetErrorCode() == net::OK);
   CHECK_IMPLIES(navigation_handle->HasCommittedErrorPage(),
                 navigation_handle->GetNetErrorCode() != net::OK);
+  CHECK_EQ(navigation_handle->GetWebContents(), web_contents());
 
   ongoing_committed_navigations_.insert(navigation_handle);
 }
@@ -169,6 +172,7 @@ void WebContentsObserverSanityChecker::DidFinishNavigation(
                 navigation_handle->GetNetErrorCode() == net::OK);
   CHECK_IMPLIES(navigation_handle->HasCommittedErrorPage(),
                 navigation_handle->GetNetErrorCode() != net::OK);
+  CHECK_EQ(navigation_handle->GetWebContents(), web_contents());
 
   if (NavigationIsOngoingAndCommitted(navigation_handle))
     ongoing_committed_navigations_.erase(navigation_handle);