[content] Make NavigateToURLFromRenderer work for same-document navigations

Currently, renderer-initiated same-document navigation using
NavigateToURLFromRenderer results in runloop timeout as
TestFrameNavigationObserver::DidStartNavigation is excluded for
SameDocumentNavigations.

This CL proposes a fix to this scenario.

Bug: 1065868
Change-Id: I9d2e7c619f3fce756d3b3f6d2196aa86820208d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2127028
Commit-Queue: Sreeja Kamishetty <sreejakshetty@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757017}

content/browser/back_forward_cache_browsertest.cc

@@ -3860,8 +3860,7 @@ IN_PROC_BROWSER_TEST_F(BackForwardCacheBrowserTest, MetricsNotRecorded) {
   EXPECT_TRUE(WaitForLoadStop(shell()->web_contents()));
 
   // 3) Navigate to B#2 (same document navigation).
-  EXPECT_TRUE(ExecJs(shell(), JsReplace("location = $1", url_b2.spec())));
-  EXPECT_TRUE(WaitForLoadStop(shell()->web_contents()));
+  EXPECT_TRUE(NavigateToURLFromRenderer(shell(), url_b2));
 
   // 4) Go back to B.
   web_contents()->GetController().GoBack();

content/public/test/test_frame_navigation_observer.cc

@@ -54,8 +54,7 @@ void TestFrameNavigationObserver::WaitForCommit() {
 void TestFrameNavigationObserver::DidStartNavigation(
     NavigationHandle* navigation_handle) {
   last_navigation_succeeded_ = false;
-  if (!navigation_handle->IsSameDocument() &&
-      navigation_handle->GetFrameTreeNodeId() == frame_tree_node_id_) {
+  if (navigation_handle->GetFrameTreeNodeId() == frame_tree_node_id_) {
     navigation_started_ = true;
     has_committed_ = false;
   }