Use css-device-adapt constraining for legacy viewport tags.

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index bcfa7c3158c8ce8494405d14230a87912344b255..8ed9f56a3661dd42371c092483d157cfcd4aea9d 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -3015,9 +3015,13 @@ void WebViewImpl::updatePageDefinedPageScaleConstraints(const ViewportArguments&
         return;
 
     ViewportArguments adjustedArguments = arguments;
-    if (settingsImpl()->viewportMetaLayoutSizeQuirk() && adjustedArguments.type == ViewportArguments::ViewportMeta)
-        adjustedArguments.type = ViewportArguments::ViewportMetaLayoutSizeQuirk;
-    m_pageScaleConstraintsSet.updatePageDefinedConstraints(adjustedArguments, m_size, page()->settings().layoutFallbackWidth());
+    if (settingsImpl()->viewportMetaLayoutSizeQuirk() && adjustedArguments.type == ViewportArguments::ViewportMeta) {
+        if (adjustedArguments.maxWidth.type() == ExtendToZoom)
+            adjustedArguments.maxWidth = Length(); // auto
+        adjustedArguments.minWidth = adjustedArguments.maxWidth;
+        adjustedArguments.minHeight = adjustedArguments.maxHeight;
+    }
+    m_pageScaleConstraintsSet.updatePageDefinedConstraints(adjustedArguments, m_size);
 
     if (settingsImpl()->supportDeprecatedTargetDensityDPI())
         m_pageScaleConstraintsSet.adjustPageDefinedConstraintsForAndroidWebView(adjustedArguments, m_size, page()->settings().layoutFallbackWidth(), deviceScaleFactor(), page()->settings().useWideViewport(), page()->settings().loadWithOverviewMode());
@@ -4129,7 +4133,7 @@ void WebViewImpl::pointerLockMouseEvent(const WebInputEvent& event)
 bool WebViewImpl::shouldDisableDesktopWorkarounds()
 {
     ViewportArguments arguments = mainFrameImpl()->frame()->document()->viewportArguments();
-    return arguments.width == ViewportArguments::ValueDeviceWidth || !arguments.userZoom
+    return arguments.maxWidth.isViewportPercentage() || !arguments.userZoom
         || (arguments.minZoom == arguments.maxZoom && arguments.minZoom != ViewportArguments::ValueAuto);
 }