[Live Caption] Introduce new media switch

kLiveCaptionSystemWideOnChromeOS.

Introduce a new media switch for the M2 launch of Live Caption.
In that launch, Live Caption will run system-wide on ChromeOS, as
opposed to just in the browser.

Bug: 1055150
Change-Id: I79176e94201edffe541db266422c79e4c264feff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2619943Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Abigail Klein <abigailbklein@google.com>
Cr-Commit-Position: refs/heads/master@{#842208}

media/base/media_switches.cc

@@ -498,6 +498,10 @@ const base::Feature kLiveCaption{"LiveCaption",
 const base::Feature kUseSodaForLiveCaption{"UseSodaForLiveCaption",
                                            base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Live Caption runs system-wide on ChromeOS, as opposed to just in the browser.
+const base::Feature kLiveCaptionSystemWideOnChromeOS{
+    "LiveCaptionSystemWideOnChromeOS", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Prevents UrlProvisionFetcher from making a provisioning request. If
 // specified, any provisioning request made will not be sent to the provisioning
 // server, and the response will indicate a failure to communicate with the

media/base/media_switches.h

@@ -145,6 +145,7 @@ MEDIA_EXPORT extern const base::Feature
 MEDIA_EXPORT extern const base::Feature kKaleidoscopeModule;
 MEDIA_EXPORT extern const base::Feature kKaleidoscopeModuleCacheOnly;
 MEDIA_EXPORT extern const base::Feature kLiveCaption;
+MEDIA_EXPORT extern const base::Feature kLiveCaptionSystemWideOnChromeOS;
 MEDIA_EXPORT extern const base::Feature kLowDelayVideoRenderingOnLiveStream;
 MEDIA_EXPORT extern const base::Feature kMediaCapabilitiesQueryGpuFactories;
 MEDIA_EXPORT extern const base::Feature kMediaCapabilitiesWithParameters;