Enable creation of offscreen contexts which own their backing surface.

ui/gl/init/gl_factory_x11.cc

Index: ui/gl/init/gl_factory_x11.cc
diff --git a/ui/gl/init/gl_factory_x11.cc b/ui/gl/init/gl_factory_x11.cc
index 88f86206e900cc5ece1eb3e89886edac3122fa31..f36fb176d42f2c08681bb26e731986ade17fde23 100644
--- a/ui/gl/init/gl_factory_x11.cc
+++ b/ui/gl/init/gl_factory_x11.cc
@@ -87,14 +87,23 @@ scoped_refptr<GLSurface> CreateViewGLSurface(gfx::AcceleratedWidget window) {
 
 scoped_refptr<GLSurface> CreateOffscreenGLSurface(const gfx::Size& size) {
   TRACE_EVENT0("gpu", "gl::init::CreateOffscreenGLSurface");
+  scoped_refptr<GLSurface> surface =
+      CreateUninitializedOffscreenGLSurface(size);
+  if (surface && GetGLImplementation() != kGLImplementationMockGL)
+    InitializeGLSurface(surface);
+  return surface;
+}
+
+scoped_refptr<GLSurface> CreateUninitializedOffscreenGLSurface(
+    const gfx::Size& size) {
+  TRACE_EVENT0("gpu", "gl::init::CreateUninitializedOffscreenGLSurface");
   switch (GetGLImplementation()) {
     case kGLImplementationOSMesaGL:
-      return InitializeGLSurface(
-          new GLSurfaceOSMesa(GLSurface::SURFACE_OSMESA_RGBA, size));
+      return new GLSurfaceOSMesa(GLSurface::SURFACE_OSMESA_RGBA, size);
     case kGLImplementationDesktopGL:
-      return InitializeGLSurface(new UnmappedNativeViewGLSurfaceGLX(size));
+      return new UnmappedNativeViewGLSurfaceGLX(size);
     case kGLImplementationEGLGLES2:
-      return InitializeGLSurface(new PbufferGLSurfaceEGL(size));
+      return new PbufferGLSurfaceEGL(size);
     case kGLImplementationMockGL:
       return new GLSurfaceStub;
     default: