[DirectWrite] Limit noSubpixelForSmallSizeFont to low-DPI

Source/platform/fonts/win/FontPlatformDataWin.cpp

Index: Source/platform/fonts/win/FontPlatformDataWin.cpp
diff --git a/Source/platform/fonts/win/FontPlatformDataWin.cpp b/Source/platform/fonts/win/FontPlatformDataWin.cpp
index 398088717b3f0b834be87889025c04bfca422e70..621e25263c1704bd76dfaa602598f7212f50d097 100644
--- a/Source/platform/fonts/win/FontPlatformDataWin.cpp
+++ b/Source/platform/fonts/win/FontPlatformDataWin.cpp
@@ -64,13 +64,20 @@ void FontPlatformData::setupPaint(SkPaint* paint, GraphicsContext* context) cons
 
     if (ts >= m_minSizeForAntiAlias) {
 
-        // Subpixel text positioning looks pretty bad without font smoothing.
-        // Disable it unless some type of font smoothing is used. As most tests
-        // run without font smoothing we enable it for tests to ensure we get
-        // good test coverage matching the more common smoothing enabled
-        // behavior.
-        if (m_useSubpixelPositioning && ts >= m_minSizeForSubpixel
-            && ((textFlags & SkPaint::kAntiAlias_Flag) || LayoutTestSupport::isRunningLayoutTest()))
+        if (m_useSubpixelPositioning
+            // Disable subpixel text for certain older fonts at smaller sizes as
+            // they tend to get quite blurry at non-integer sizes and positions.
+            // For high-DPI this workaround isn't required.
+            && (ts >= m_minSizeForSubpixel
+                || FontCache::fontCache()->deviceScaleFactor() >= 1.5)
+
+            // Subpixel text positioning looks pretty bad without font
+            // smoothing. Disable it unless some type of font smoothing is used.
+            // As most tests run without font smoothing we enable it for tests
+            // to ensure we get good test coverage matching the more common
+            // smoothing enabled behavior.
+            && ((textFlags & SkPaint::kAntiAlias_Flag)
+                || LayoutTestSupport::isRunningLayoutTest()))
             flags |= SkPaint::kSubpixelText_Flag;
 
         // Only set painting flags when we're actually painting.