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

ui/base/material_design/material_design_controller.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/trace_event/trace_event.h"
 #include "ui/base/material_design/material_design_controller.h"
@@ skipping 18 matching lines @@
 
 MaterialDesignController::Mode MaterialDesignController::mode_ =
     MaterialDesignController::Mode::NON_MATERIAL;
 
 // static
 void MaterialDesignController::Initialize() {
   TRACE_EVENT0("startup", "MaterialDesignController::InitializeMode");
   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(
           switches::kTopChromeMD);
 
   if (switch_value == switches::kTopChromeMDMaterial) {
     SetMode(Mode::MATERIAL_NORMAL);
   } else if (switch_value == switches::kTopChromeMDMaterialHybrid) {
     SetMode(Mode::MATERIAL_HYBRID);
   } else if (switch_value == switches::kTopChromeMDNonMaterial) {
@@ skipping 60 matching lines @@
   is_mode_initialized_ = false;
 }
 
 // static
 void MaterialDesignController::SetMode(MaterialDesignController::Mode mode) {
   mode_ = mode;
   is_mode_initialized_ = true;
 }
 
 }  // namespace ui