Initialize the message center as part of the testing browser process

chrome/browser/usb/web_usb_detector_unittest.cc

Index: chrome/browser/usb/web_usb_detector_unittest.cc
diff --git a/chrome/browser/usb/web_usb_detector_unittest.cc b/chrome/browser/usb/web_usb_detector_unittest.cc
index dd410a289278e9dd92a7b055d1422952b548b174..36315d3c50669d5df22aad9bf696fcf07b3004a9 100644
--- a/chrome/browser/usb/web_usb_detector_unittest.cc
+++ b/chrome/browser/usb/web_usb_detector_unittest.cc
@@ -7,6 +7,7 @@
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
+#include "chrome/browser/browser_process.h"
 #include "chrome/browser/usb/web_usb_detector.h"
 #include "device/base/mock_device_client.h"
 #include "device/usb/mock_usb_device.h"
@@ -41,12 +42,11 @@ class WebUsbDetectorTest : public testing::Test {
   ~WebUsbDetectorTest() override = default;
 
   void SetUp() override {
-    message_center::MessageCenter::Initialize();
-    message_center_ = message_center::MessageCenter::Get();
+    message_center_ = g_browser_process->message_center();
     ASSERT_TRUE(message_center_ != nullptr);
   }
 
-  void TearDown() override { message_center::MessageCenter::Shutdown(); }
+  void TearDown() override { message_center_ = nullptr; }
 
  protected:
   device::MockDeviceClient device_client_;