Experiment with more aggressive MSE GC on memory pressure

media/base/media_switches.cc

Index: media/base/media_switches.cc
diff --git a/media/base/media_switches.cc b/media/base/media_switches.cc
index 5299efe7794b19241204fbc1ecaf68ee281732eb..bbceba7012d2470ddee4c808e01efb41edc861ca 100644
--- a/media/base/media_switches.cc
+++ b/media/base/media_switches.cc
@@ -164,6 +164,17 @@ const base::Feature kResumeBackgroundVideo {
 const base::Feature kBackgroundVideoTrackOptimization{
     "BackgroundVideoTrackOptimization", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Reduce memory limits for MSE SourceBuffers under memory pressure conditions.

[DaleCurtis, 2017/01/26 19:24:50]

Probably would be easier to have a single feature with multiple values.

[servolk, 2017/01/26 19:38:31]

IIUC the base::Feature is only binary (enabled/disabled), I don't see a way to
use custom values in there. I guess we could use custom command-line param, but
I'm not sure if that's better than reusing the standard base::Feature and
base::Feature list functionality.

[DaleCurtis, 2017/01/26 19:48:33]

Sure it's binary only, but you can use variations to modify the feature,

https://cs.chromium.org/chromium/src/components/variations/variations_associa...

See an example of what we did for keyframe_distance here:
https://cs.chromium.org/search/?q=keyframe_distance

The key bit is this will allow you to do easier comparisons across your
experiment groups. You can't accurate compare the two groups otherwise.

+// This will relieve memory pressure by releasing stale data from MSE buffers.
+const base::Feature kReduceMSEBuffersOnMemoryPressure{
+    "ReduceMSEBuffersOnMemoryPressure", base::FEATURE_DISABLED_BY_DEFAULT};
+
+// Perform MSE garbage collection immediately when we get notification about
+// critical memory pressure, instead of waiting for the next SourceBuffer append
+// operation.
+const base::Feature kMSEInstantGCOnMemoryPressure{
+    "MSEInstantGCOnMemoryPressure", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Use shared block-based buffering for media.
 const base::Feature kUseNewMediaCache{"use-new-media-cache",
                                       base::FEATURE_ENABLED_BY_DEFAULT};