[PM] Switch Dynamic Tcmalloc to CrOS only

Finch experiments have shown this has more of a benefit on CrOS rather than
linux. We suspect this is because CrOS devices tend to have much lower RAM
configurations. So we've decided to ship only on CrOS.

This CL will officially make this feature only available to CrOS.

BUG=chromium:993569

Change-Id: Ib86316564735b3b9d790f2101dd7d8e185bfcf11
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2250670
Reviewed-by: Matthew Denton <[email protected]>
Reviewed-by: Chris Hamilton <[email protected]>
Commit-Queue: Brian Geffon <[email protected]>
Cr-Commit-Position: refs/heads/master@{#781011}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index f3e6160..64f7921b 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2680,14 +2680,12 @@
      flag_descriptions::kPluginVmShowMicrophonePermissionsDescription, kOsCrOS,
      FEATURE_VALUE_TYPE(
          chromeos::features::kPluginVmShowMicrophonePermissions)},
-#endif  // OS_CHROMEOS
-#if defined(OS_CHROMEOS) || defined(OS_LINUX)
 #if BUILDFLAG(USE_TCMALLOC)
     {"dynamic-tcmalloc-tuning", flag_descriptions::kDynamicTcmallocName,
-     flag_descriptions::kDynamicTcmallocDescription, kOsCrOS | kOsLinux,
+     flag_descriptions::kDynamicTcmallocDescription, kOsCrOS,
      FEATURE_VALUE_TYPE(performance_manager::features::kDynamicTcmallocTuning)},
 #endif  // BUILDFLAG(USE_TCMALLOC)
-#endif  // OS_CHROMEOS || OS_LINUX
+#endif  // OS_CHROMEOS
 #if defined(OS_ANDROID)
     {"enable-credit-card-assist", flag_descriptions::kCreditCardAssistName,
      flag_descriptions::kCreditCardAssistDescription, kOsAndroid,