bluetooth: Added Linux platform to Web Bluetooth flag

BUG=570344

Review URL: https://codereview.chromium.org/1598943005

Cr-Commit-Position: refs/heads/master@{#370139}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index a2b41f50..470ec6f 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -755,7 +755,7 @@
     {"enable-web-bluetooth",
      IDS_FLAGS_WEB_BLUETOOTH_NAME,
      IDS_FLAGS_WEB_BLUETOOTH_DESCRIPTION,
-     kOsCrOS | kOsMac | kOsAndroid,
+     kOsCrOS | kOsMac | kOsAndroid | kOsLinux,
      SINGLE_VALUE_TYPE(switches::kEnableWebBluetooth)},
 #if defined(ENABLE_EXTENSIONS)
     {"enable-ble-advertising-in-apps",