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

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index f4e161c00ad670a1bc8f27728e1f3aa15c9dd9c8..036383b759489cc719371eac9473b02b55ac487a 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -360,6 +360,7 @@ WebViewImpl::WebViewImpl(WebViewClient* client)
     , m_spellCheckerClientImpl(this)
     , m_storageClientImpl(this)
     , m_fixedLayoutSizeLock(false)
+    , m_forceZeroLayoutHeight(false)
     , m_shouldAutoResize(false)
     , m_zoomLevel(0)
     , m_minimumZoomLevel(zoomFactorToZoomLevel(minTextSizeMultiplier))
@@ -3049,6 +3050,9 @@ void WebViewImpl::updateMainFrameLayoutSize()
         }
     }
 
+    if (m_forceZeroLayoutHeight)
+        layoutSize.height = 0;
+
     view->setLayoutSize(layoutSize);
 }
 
@@ -3106,6 +3110,15 @@ void WebViewImpl::resetScrollAndScaleState()
         view->cacheCurrentScrollPosition();
 }
 
+void WebViewImpl::setForceZeroLayoutHeight(bool enable)
+{
+    if (m_forceZeroLayoutHeight == enable)
+        return;
+
+    m_forceZeroLayoutHeight = enable;
+    updateMainFrameLayoutSize();
+}
+
 void WebViewImpl::setFixedLayoutSize(const WebSize& layoutSize)
 {
     if (!page() || !page()->mainFrame()->isLocalFrame())