[Mac][Material Design] Make Material Design the default.

ui/base/material_design/material_design_controller.cc

Index: ui/base/material_design/material_design_controller.cc
diff --git a/ui/base/material_design/material_design_controller.cc b/ui/base/material_design/material_design_controller.cc
index f4e633612d67d606368caf25f24105ff025f85ee..f2fd577b92e34dec8b2edd08203fbdd20e5be177 100644
--- a/ui/base/material_design/material_design_controller.cc
+++ b/ui/base/material_design/material_design_controller.cc
@@ -36,6 +36,8 @@ void MaterialDesignController::Initialize() {
   CHECK(!is_mode_initialized_);
 #if !defined(ENABLE_TOPCHROME_MD)
   SetMode(Mode::NON_MATERIAL);
+#elif defined(OS_MACOSX)
+  SetMode(Mode::MATERIAL_NORMAL);

[tdanderson, 2016/05/05 14:56:55]

From my reading of the code, it looks like OSX does define the compile-time flag
ENABLE_TOPCHROME_MD (see src/build/config/ui.gni). So instead of calling
SetMode() here, you should add an #elif case for OSX at the end of DefaultMode()
to return MATERIAL_NORMAL.

[shrike, 2016/05/05 16:10:51]

Thank you. I felt like I had seen per-platform #defines somewhere but they
weren't where I had expected to find them.

 #else
   const std::string switch_value =
       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(