Add Settings::deviceScaleAdjustment.

Source/core/rendering/TextAutosizer.cpp

Index: Source/core/rendering/TextAutosizer.cpp
diff --git a/Source/core/rendering/TextAutosizer.cpp b/Source/core/rendering/TextAutosizer.cpp
index 0424b5a6e365d27923be17813dc1644291d63025..044d80e93749abd26dc2b782ab85757f4b2ac61d 100644
--- a/Source/core/rendering/TextAutosizer.cpp
+++ b/Source/core/rendering/TextAutosizer.cpp
@@ -208,6 +208,12 @@ float TextAutosizer::clusterMultiplier(WritingMode writingMode, const TextAutosi
 
     float multiplier = logicalClusterWidth / logicalWindowWidth;
     multiplier *= m_document->settings()->textAutosizingFontScaleFactor();
+
+    // If the page has a meta viewport or @viewport, don't apply the device scale adjustment.
+    const ViewportDescription& viewportDescription = m_document->page()->mainFrame()->document()->viewportDescription();
+    if (!viewportDescription.isSpecifiedByAuthor()) {
+        multiplier *= m_document->settings()->deviceScaleAdjustment();
+    }
     return std::max(1.0f, multiplier);
 }