FrameTree::Find only searches relative to local frames.

components/printing/test/print_web_view_helper_browsertest.cc

Index: components/printing/test/print_web_view_helper_browsertest.cc
diff --git a/components/printing/test/print_web_view_helper_browsertest.cc b/components/printing/test/print_web_view_helper_browsertest.cc
index 0cd8115925d9340af1099f7d11340df55b785ff0..3c708f782108dc32617401b50847f0e8b7218437 100644
--- a/components/printing/test/print_web_view_helper_browsertest.cc
+++ b/components/printing/test/print_web_view_helper_browsertest.cc
@@ -413,7 +413,9 @@ TEST_F(MAYBE_PrintWebViewHelperTest, PrintWithIframe) {
   // Find the frame and set it as the focused one.  This should mean that that
   // the printout should only contain the contents of that frame.
   auto* web_view = view_->GetWebView();
-  WebFrame* sub1_frame = web_view->FindFrameByName(WebString::FromUTF8("sub1"));
+  WebFrame* sub1_frame =
+      web_view->MainFrame()->ToWebLocalFrame()->FindFrameByName(
+          WebString::FromUTF8("sub1"));

[Łukasz Anforowicz, 2017/05/26 16:38:40]

ToWebLocalFrame() above is okay, because otherwise the old code would have
returned null and ASSERT_TRUE(sub1_frame) below would have fired.

   ASSERT_TRUE(sub1_frame);
   web_view->SetFocusedFrame(sub1_frame);
   ASSERT_NE(web_view->FocusedFrame(), web_view->MainFrame());