Use browser top chrome material design by default on Chrome OS

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 "ui/base/material_design/material_design_controller.h"
 #include "ui/base/ui_base_switches.h"
@@ skipping 10 matching lines @@
     InitializeMode();
   CHECK(is_mode_initialized_);
   return mode_;
 }
 
 bool MaterialDesignController::IsModeMaterial() {
   return GetMode() == Mode::MATERIAL_NORMAL ||
          GetMode() == Mode::MATERIAL_HYBRID;
 }
 
+MaterialDesignController::Mode MaterialDesignController::DefaultMode() {
+#if defined(OS_CHROMEOS)
+  return Mode::MATERIAL_NORMAL;
+#else
+  return Mode::NON_MATERIAL;
+#endif  // defined(OS_CHROMEOS)
+}
+
 void MaterialDesignController::InitializeMode() {
 #if !defined(ENABLE_TOPCHROME_MD)
   SetMode(Mode::NON_MATERIAL);
 #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) {
     SetMode(Mode::NON_MATERIAL);
   } else {
-    LOG(ERROR) << "Invalid value='" << switch_value
-               << "' for command line switch '" << switches::kTopChromeMD
-               << "'.";
-    SetMode(Mode::NON_MATERIAL);
+    if (!switch_value.empty()) {
+      LOG(ERROR) << "Invalid value='" << switch_value
+                 << "' for command line switch '" << switches::kTopChromeMD
+                 << "'.";
+    }
+    SetMode(DefaultMode());
   }
 #endif  // !defined(ENABLE_TOPCHROME_MD)
 }
 
 void MaterialDesignController::UninitializeMode() {
   MaterialDesignController::SetMode(
       MaterialDesignController::Mode::NON_MATERIAL);
   is_mode_initialized_ = false;
 }
 
 void MaterialDesignController::SetMode(MaterialDesignController::Mode mode) {
   mode_ = mode;
   is_mode_initialized_ = true;
 }
 
 }  // namespace ui