Revert "Add RuntimeEnabledFeature for retargeting _blank navigations to _top"

This reverts commit 2c8d5bfc.

Reason for revert: Looks like this doesn't do what I hoped it would (The sites I was testing on weren't sufficient).

var foo = window.open('foo.html); will set the target to "_blank" implicitly.

Original change's description:
> Add RuntimeEnabledFeature for retargeting _blank navigations to _top
> 
> See bug for context.
> 
> Notry=true
> 
> Bug: 961035
> Change-Id: Icfb0b2e62dbe7a07321d5fefee4a8cbeec42451f
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1674677
> Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
> Reviewed-by: Daniel Cheng <dcheng@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#673535}

TBR=dcheng@chromium.org,mthiesse@chromium.org,clamy@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 961035
Change-Id: I906713ed297ea8894650563db7036d6baf56112c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1695697Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676109}

third_party/blink/renderer/core/exported/web_view_test.cc

@@ -3624,36 +3624,6 @@ TEST_F(WebViewTest, FocusExistingFrameOnNavigate) {
   web_view_helper.Reset();  // Remove dependency on locally scoped client.
 }
 
-class RedirectBlankToTopClient
-    : public ViewCreatingWebViewClient,
-      private ScopedRedirectBlankNavigationToTopForTest {
- public:
-  RedirectBlankToTopClient()
-      : ScopedRedirectBlankNavigationToTopForTest(true) {}
-};
-
-TEST_F(WebViewTest, BlankRedirectsToTop) {
-  RedirectBlankToTopClient client;
-  frame_test_helpers::WebViewHelper web_view_helper;
-  WebViewImpl* web_view_impl = web_view_helper.Initialize(nullptr, &client);
-  WebLocalFrameImpl* frame = web_view_impl->MainFrameImpl();
-  frame->SetName("_start");
-
-  // Make a request that will open a new window
-  WebURLRequest web_url_request(KURL("about:blank"));
-  FrameLoadRequest request(nullptr, web_url_request.ToResourceRequest());
-  const FrameTree::FindResult& found_frame =
-      To<LocalFrame>(web_view_impl->GetPage()->MainFrame())
-          ->Tree()
-          .FindOrCreateFrameForNavigation(request, "_blank");
-  ASSERT_FALSE(client.CreatedWebView());
-  WebLocalFrameImpl* found_local_frame = WebLocalFrameImpl::FromFrame(
-      DynamicTo<LocalFrame>(found_frame.frame.Get()));
-  EXPECT_EQ(found_local_frame, frame);
-
-  web_view_helper.Reset();  // Remove dependency on locally scoped client.
-}
-
 class ViewReusingWebViewClient : public frame_test_helpers::TestWebViewClient {
  public:
   ViewReusingWebViewClient() = default;

third_party/blink/renderer/core/page/frame_tree.cc

@@ -242,17 +242,10 @@ Frame* FrameTree::FindFrameForNavigationInternal(const AtomicString& name,
   if (EqualIgnoringASCIICase(name, "_parent"))
     return Parent() ? Parent() : this_frame_.Get();
 
-  if (EqualIgnoringASCIICase(name, "_blank")) {
-    if (RuntimeEnabledFeatures::RedirectBlankNavigationToTopEnabled()) {
-      // TODO(mthiesse): Only apply this behavior to navigations without
-      // rel=opener once
-      // https://html.spec.whatwg.org/multipage/links.html#link-type-opener is
-      // implemented.
-      return &Top();
-    } else {
-      return nullptr;
-    }
-  }
+  // Since "_blank" should never be any frame's name, the following just amounts
+  // to an optimization.
+  if (EqualIgnoringASCIICase(name, "_blank"))
+    return nullptr;
 
   // Search subtree starting with this frame first.
   for (Frame* frame = this_frame_; frame;

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1266,9 +1266,6 @@
       name: "RasterInducingScroll",
       status: "experimental",
     },
-    {
-      name: "RedirectBlankNavigationToTop",
-    },
     {
       name: "ReducedReferrerGranularity",
     },