Add a force-layout-height-to-zero layout mode to WebViewImpl

Source/web/tests/WebFrameTest.cpp

Index: Source/web/tests/WebFrameTest.cpp
diff --git a/Source/web/tests/WebFrameTest.cpp b/Source/web/tests/WebFrameTest.cpp
index 8bdd4513fa124eaef83320487080146863deb82d..9e2e0ff81cbff4568c8a518e5a163a37ea5279e8 100644
--- a/Source/web/tests/WebFrameTest.cpp
+++ b/Source/web/tests/WebFrameTest.cpp
@@ -1371,6 +1371,40 @@ TEST_F(WebFrameTest, WideViewportInitialScaleDoesNotExpandFixedLayoutWidth)
     EXPECT_EQ(0.5f, webViewHelper.webView()->pageScaleFactor());
 }
 
+TEST_F(WebFrameTest, SetForceZeroLayoutHeight)
+{
+    UseMockScrollbarSettings mockScrollbarSettings;
+    registerMockedHttpURLLoad("200-by-300.html");
+
+    FixedLayoutTestWebViewClient client;
+    client.m_screenInfo.deviceScaleFactor = 1;
+    int viewportWidth = 640;
+    int viewportHeight = 480;
+
+    FrameTestHelpers::WebViewHelper webViewHelper;
+
+    webViewHelper.initializeAndLoad(m_baseURL + "200-by-300.html", true, 0, &client, enableViewportSettings);
+    webViewHelper.webView()->resize(WebSize(viewportWidth, viewportHeight));
+    webViewHelper.webView()->layout();
+
+    EXPECT_EQ(viewportHeight, webViewHelper.webViewImpl()->mainFrameImpl()->frameView()->layoutSize().height());
+    webViewHelper.webView()->settings()->setForceZeroLayoutHeight(true);
+    EXPECT_TRUE(webViewHelper.webViewImpl()->mainFrameImpl()->frameView()->needsLayout());
+
+    EXPECT_EQ(0, webViewHelper.webViewImpl()->mainFrameImpl()->frameView()->layoutSize().height());
+
+    webViewHelper.webView()->resize(WebSize(viewportWidth, viewportHeight * 2));
+    EXPECT_FALSE(webViewHelper.webViewImpl()->mainFrameImpl()->frameView()->needsLayout());
+    EXPECT_EQ(0, webViewHelper.webViewImpl()->mainFrameImpl()->frameView()->layoutSize().height());
+
+    webViewHelper.webView()->resize(WebSize(viewportWidth * 2, viewportHeight));
+    webViewHelper.webView()->layout();
+    EXPECT_EQ(0, webViewHelper.webViewImpl()->mainFrameImpl()->frameView()->layoutSize().height());
+
+    webViewHelper.webView()->settings()->setForceZeroLayoutHeight(false);
+    EXPECT_EQ(viewportHeight, webViewHelper.webViewImpl()->mainFrameImpl()->frameView()->layoutSize().height());
+}
+
 TEST_F(WebFrameTest, WideViewportAndWideContentWithInitialScale)
 {
     UseMockScrollbarSettings mockScrollbarSettings;