Support offscreen contexts which own their backing surface

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
index 010b60b6f884accdd1487866ab9224937604af86..436d5d83a6a8d8b185fd453c3f66f2926ba82ee7 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -25,6 +25,7 @@
 
 #include "modules/webgl/WebGLRenderingContextBase.h"
 
+#include <memory>
 #include "bindings/core/v8/ExceptionMessages.h"
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptWrappableVisitor.h"
@@ -47,6 +48,7 @@
 #include "core/layout/LayoutBox.h"
 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
+#include "core/origin_trials/OriginTrials.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "modules/webgl/ANGLEInstancedArrays.h"
 #include "modules/webgl/EXTBlendMinMax.h"
@@ -102,7 +104,6 @@
 #include "wtf/text/StringBuilder.h"
 #include "wtf/text/StringUTF8Adaptor.h"
 #include "wtf/typed_arrays/ArrayBufferContents.h"
-#include <memory>
 
 namespace blink {
 
@@ -624,6 +625,24 @@ WebGLRenderingContextBase::createContextProviderInternal(
 
   Platform::ContextAttributes contextAttributes =
       toPlatformContextAttributes(attributes, webGLVersion);
+
+  // If there's a possibility this context may be used with WebVR make sure it
+  // is created with an offscreen surface that can be swapped out for a
+  // VR-specific surface if needed. We can only check the origin trial
+  // if called with a scriptState, not for a canvas.

[amp, 2017/02/15 20:04:22]

Comment seems out of sync with code which does check the canvas for an origin
trial.

[klausw, 2017/02/15 20:21:15]

Done.

+  //
+  // At this time, treat this as an experimental rendering optimization
+  // that needs a separate opt-in. See crbug.com/691102 for details.
+  if (RuntimeEnabledFeatures::webVRExperimentalRenderingEnabled()) {
+    if (RuntimeEnabledFeatures::webVREnabled() ||
+        OriginTrials::webVREnabled(
+            canvas ? canvas->document().getExecutionContext()
+                   : scriptState->getExecutionContext())) {
+      DVLOG(1) << "Requesting supportOwnOffscreenSurface";
+      contextAttributes.supportOwnOffscreenSurface = true;
+    }
+  }
+
   Platform::GraphicsInfo glInfo;
   std::unique_ptr<WebGraphicsContext3DProvider> contextProvider;
   const auto& url = canvas ? canvas->document().topDocument().url()