Avoid auto-resize re-entrancy problems.

Source/web/tests/WebViewTest.cpp

Index: Source/web/tests/WebViewTest.cpp
diff --git a/Source/web/tests/WebViewTest.cpp b/Source/web/tests/WebViewTest.cpp
index 35feefd9540a1cd157e02b3457f4e3f4021d5ce3..c1c2efc2a88bf50d850412044453f4da43b0e196 100644
--- a/Source/web/tests/WebViewTest.cpp
+++ b/Source/web/tests/WebViewTest.cpp
@@ -82,6 +82,7 @@
 #include <gtest/gtest.h>
 
 using namespace blink;
+using blink::FrameTestHelpers::loadFrame;
 using blink::FrameTestHelpers::runPendingTasks;
 using blink::URLTestHelpers::toKURL;
 
@@ -2155,4 +2156,20 @@ TEST_F(WebViewTest, CompareSelectAllToContentAsText)
     EXPECT_EQ(expected, actual);
 }
 
+TEST_F(WebViewTest, AutoResizeSubtreeLayout)
+{
+    std::string url = m_baseURL + "subtree-layout.html";
+    URLTestHelpers::registerMockedURLLoad(toKURL(url), "subtree-layout.html");
+    WebView* webView = m_webViewHelper.initialize(true);
+
+    webView->enableAutoResizeMode(WebSize(200, 200), WebSize(200, 200));
+    loadFrame(webView->mainFrame(), url);
+
+    blink::FrameView* frameView = m_webViewHelper.webViewImpl()->mainFrameImpl()->frameView();
+
+    // Auto-resizing used to ASSERT(needsLayout()) in RenderBlockFlow::layout. This EXPECT is
+    // merely a dummy. The real test is that we don't trigger asserts in debug builds.
+    EXPECT_FALSE(frameView->needsLayout());
+};
+
 } // namespace