Set Control.DefaultFont to SystemFonts.MessageBoxFont

This change ensures Segoe UI is used by default on Windows Vista
and later, while still not breaking compatibility with Windows XP
or systems compatible with it.

Author: wjk

src/System.Windows.Forms/src/System/Windows/Forms/Control.cs

@@ -2274,7 +2274,7 @@ public static Font DefaultFont
             {
                 if (defaultFont == null)
                 {
-                    defaultFont = SystemFonts.DefaultFont;
+                    defaultFont = SystemFonts.MessageBoxFont;
                     Debug.Assert(defaultFont != null, "defaultFont wasn't set!");
                 }
 

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/ComboBoxTests.cs

@@ -375,7 +375,7 @@ public void Font_SetWithHandler_CallsFontChanged()
             control.FontChanged += handler;
 
             // Set different.
-            Font font1 = SystemFonts.MenuFont;
+            Font font1 = new Font("Arial", 8.25f);
             control.Font = font1;
             Assert.Same(font1, control.Font);
             Assert.Equal(1, callCount);

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/DataGridViewRowTests.cs

@@ -948,7 +948,7 @@ public static IEnumerable<object[]> Height_NeedsHeightInfo_TestData()
                     ColumnCount = 1,
                     AutoSizeRowsMode = DataGridViewAutoSizeRowsMode.AllCells
                 },
-                22, 0, 22
+                25, 0, 25
             };
             yield return new object[] { new DataGridView { ColumnCount = 1, VirtualMode = true }, 6, 1, 5 };
 

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/ListBoxTests.cs

@@ -376,7 +376,7 @@ public void Font_SetWithHandler_CallsFontChanged()
             control.FontChanged += handler;
 
             // Set different.
-            Font font1 = SystemFonts.MenuFont;
+            Font font1 = new Font("Arial", 8.25f);
             control.Font = font1;
             Assert.Same(font1, control.Font);
             Assert.Equal(1, callCount);