GMC: Disable by default

Since we're not releasing GMC in M78, this CL disables GMC by default.

Bug: 1007486
Change-Id: I8c0131710abbb393faad4d739fac53aca41e8939
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1823437
Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700047}

media/base/media_switches.cc

@@ -304,15 +304,8 @@ const base::Feature kFallbackAfterDecodeError{"FallbackAfterDecodeError",
                                               base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Show toolbar button that opens dialog for controlling media sessions.
-const base::Feature kGlobalMediaControls {
-  "GlobalMediaControls",
-#if defined(OS_WIN) || defined(OS_MACOSX) || \
-    (defined(OS_LINUX) && !defined(OS_CHROMEOS))
-      base::FEATURE_ENABLED_BY_DEFAULT
-#else
-      base::FEATURE_DISABLED_BY_DEFAULT
-#endif
-};
+const base::Feature kGlobalMediaControls{"GlobalMediaControls",
+                                         base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Enable new cpu load estimator. Intended for evaluation in local
 // testing and origin-trial.