gpu: Add flag for enabling asynchronous worker context.

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 4516ed9924ac8cc33b90c893fb49a0c7425e95d8..e07157ba256055eaea0a70c9c7909602ffb257bf 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -381,6 +381,9 @@ const char kEnableGpuMemoryBufferVideoFrames[] =
 // impl-side painting.
 const char kEnableGpuRasterization[]        = "enable-gpu-rasterization";
 
+// Makes the worker GL context run asynchronously by using a separate stream.
+const char kEnableGpuAsyncWorkerContext[]   = "enable-gpu-async-worker-context";
+
 // When using CPU rasterizing generate low resolution tiling. Low res
 // tiles may be displayed during fast scrolls especially on slower devices.
 const char kEnableLowResTiling[] = "enable-low-res-tiling";