[Global Media Controls] Add HardwareMediaKeyHandling flag to Linux

This CL allows the HardwareMediaKeyHandling flag to show up in
chrome://flags on Linux.

Bug: 925201
Change-Id: I390a36dd25573171e7461bf1554eabb8c5944178
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1518907
Reviewed-by: Becca Hughes <[email protected]>
Commit-Queue: Tommy Steimel <[email protected]>
Cr-Commit-Position: refs/heads/master@{#640127}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index c62821d..0fe8d8f 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -3953,11 +3953,10 @@
      FEATURE_VALUE_TYPE(autofill::features::kAutofillSettingsCardTypeSplit)},
 #endif  // defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_LINUX)
 
-#if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_CHROMEOS)
+#if !defined(OS_ANDROID)
     {"hardware-media-key-handling",
      flag_descriptions::kHardwareMediaKeyHandling,
-     flag_descriptions::kHardwareMediaKeyHandlingDescription,
-     kOsWin | kOsMac | kOsCrOS,
+     flag_descriptions::kHardwareMediaKeyHandlingDescription, kOsDesktop,
      FEATURE_VALUE_TYPE(media::kHardwareMediaKeyHandling)},
 #endif