multibuffer field trial

BUG=514719

Review URL: https://codereview.chromium.org/1670753003

Cr-Commit-Position: refs/heads/master@{#374773}

content/browser/renderer_host/render_process_host_impl.cc

@@ -1503,7 +1503,6 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     // --in-process-webgl.
     switches::kUseGL,
     switches::kUseMobileUserAgent,
-    switches::kUseNewMediaCache,
     switches::kUseNormalPriorityForTileTaskWorkerThreads,
     switches::kUseRemoteCompositing,
     switches::kV,

media/base/media_switches.cc

@@ -129,7 +129,12 @@ const char kVideoUnderflowThresholdMs[] = "video-underflow-threshold-ms";
 const char kDisableRTCSmoothnessAlgorithm[] =
     "disable-rtc-smoothness-algorithm";
 
+}  // namespace switches
+
+namespace media {
+
 // Use shared block-based buffering for media.
-const char kUseNewMediaCache[] = "use-new-media-cache";
+const base::Feature kUseNewMediaCache{"use-new-media-cache",
+                                      base::FEATURE_DISABLED_BY_DEFAULT};
 
-}  // namespace switches
+}  // namespace media

media/base/media_switches.h

@@ -7,6 +7,7 @@
 #ifndef MEDIA_BASE_MEDIA_SWITCHES_H_
 #define MEDIA_BASE_MEDIA_SWITCHES_H_
 
+#include "base/feature_list.h"
 #include "build/build_config.h"
 #include "media/base/media_export.h"
 
@@ -62,8 +63,14 @@ MEDIA_EXPORT extern const char kVideoUnderflowThresholdMs[];
 
 MEDIA_EXPORT extern const char kDisableRTCSmoothnessAlgorithm[];
 
-MEDIA_EXPORT extern const char kUseNewMediaCache[];
-
 }  // namespace switches
 
+namespace media {
+
+// All features in alphabetical order. The features should be documented
+// alongside the definition of their values in the .cc file.
+MEDIA_EXPORT extern const base::Feature kUseNewMediaCache;
+
+}  // namespace media
+
 #endif  // MEDIA_BASE_MEDIA_SWITCHES_H_

media/blink/webmediaplayer_impl.cc

@@ -291,9 +291,11 @@ void WebMediaPlayerImpl::DoLoad(LoadType load_type,
     return;
   }
 
+  // TODO(hubbe): This experiment is temporary and should be removed once
+  // we have enough data to support the primacy of the new media cache.
+  // See http://crbug.com/514719 for details.
   // Otherwise it's a regular request which requires resolving the URL first.
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kUseNewMediaCache)) {
+  if (base::FeatureList::IsEnabled(kUseNewMediaCache)) {
     // Remove this when MultiBufferDataSource becomes default.
     LOG(WARNING) << "Using MultibufferDataSource";
     data_source_.reset(new MultibufferDataSource(