SecondaryUiMd on by default for CrOS

Enables Harmony dialog styling by default on Chrome OS dialogs.  Also
see launch bug crbug.com/839559.

Bug: 783540
Test: Summon any dialog (blockers of 783540) that has been Harmonized.
Verify that it has the Harmonious styling.

Change-Id: I2c9340d33d0d404edec2b110fe4dd9d6727bc645
Reviewed-on: https://chromium-review.googlesource.com/1072727Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Greg Levin <glevin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568576}

ui/base/ui_base_features.cc

@@ -46,15 +46,7 @@ const base::Feature kExperimentalUi{"ExperimentalUi",
 // Applies the material design mode to elements throughout Chrome (not just top
 // Chrome).
 const base::Feature kSecondaryUiMd = {"SecondaryUiMd",
-// Enabled by default on Windows, Mac and Desktop Linux.
-// http://crbug.com/775847.
-#if defined(OS_WIN) || defined(OS_MACOSX) || \
-    (defined(OS_LINUX) && !defined(OS_CHROMEOS))
-                                      base::FEATURE_ENABLED_BY_DEFAULT
-#else
-                                      base::FEATURE_DISABLED_BY_DEFAULT
-#endif
-};
+                                      base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Allows system keyboard event capture when |features::kKeyboardLockApi| is on.
 const base::Feature kSystemKeyboardLock{"SystemKeyboardLock",