Support offscreen contexts which own their backing surface

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index da838472d9a1087a76b4e814fe3e83dfa9de6dc7..ce1ba5f91ee2ff26da7713d0e32669549c98b76c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -96984,6 +96984,7 @@ value.
   <int value="-290672626" label="enable-asm-wasm"/>
   <int value="-288316828" label="enable-delegated-renderer"/>
   <int value="-279920685" label="affiliation-based-matching:enabled"/>
+  <int value="-279493876" label="WebVRExperimentalRendering:enabled"/>
   <int value="-278347667" label="default-tile-height"/>
   <int value="-277144896" label="enable-viewport-meta"/>
   <int value="-268357961" label="enable-feature-policy"/>
@@ -97079,6 +97080,7 @@ value.
   <int value="189728101" label="FasterLocationReload:disabled"/>
   <int value="194573877" label="MacViewsNativeDialogs:disabled"/>
   <int value="194895489" label="passive-listeners-default"/>
+  <int value="200347243" label="WebVRExperimentalRendering:disabled"/>
   <int value="201343576" label="enable-password-change-support:enabled"/>
   <int value="203776499" label="enable-virtual-keyboard-overscroll"/>
   <int value="223662457" label="BackgroundLoadingForDownloads:enabled"/>