Ignore custom offscreen surface unless explicitly opted in

gpu/ipc/service/gpu_command_buffer_stub.cc

Index: gpu/ipc/service/gpu_command_buffer_stub.cc
diff --git a/gpu/ipc/service/gpu_command_buffer_stub.cc b/gpu/ipc/service/gpu_command_buffer_stub.cc
index 6d305cf9ab99b670e9d8c743e9ad21c6cbd1161d..e5e060d364cd7b31adfc473ae7a350aaed56abd6 100644
--- a/gpu/ipc/service/gpu_command_buffer_stub.cc
+++ b/gpu/ipc/service/gpu_command_buffer_stub.cc
@@ -655,20 +655,29 @@ bool GpuCommandBufferStub::Initialize(
   decoder_->set_engine(executor_.get());
 
   if (offscreen) {
-    if (init_params.attribs.depth_size > 0) {
-      surface_format.SetDepthBits(init_params.attribs.depth_size);
+    // Do we want to create an offscreen rendering context suitable
+    // for directly drawing to a separately supplied surface? In that
+    // case, we must ensure that the surface used for context creation
+    // is compatible with the requested attributes. This is explicitly
+    // opt-in since some context such as for NaCl request custom
+    // attributes but don't expect to get their own surface, and not
+    // all surface factories support custom formats.
+    if (init_params.attribs.own_offscreen_surface) {
+      if (init_params.attribs.depth_size > 0) {
+        surface_format.SetDepthBits(init_params.attribs.depth_size);
+      }
+      if (init_params.attribs.samples > 0) {
+        surface_format.SetSamples(init_params.attribs.samples);
+      }
+      if (init_params.attribs.stencil_size > 0) {
+        surface_format.SetStencilBits(init_params.attribs.stencil_size);
+      }
+      // Currently, we can't separately control alpha channel for surfaces,
+      // it's generally enabled by default except for RGB565 and (on desktop)
+      // smaller-than-32bit formats.
+      //
+      // TODO(klausw): use init_params.attribs.alpha_size here if possible.
     }
-    if (init_params.attribs.samples > 0) {
-      surface_format.SetSamples(init_params.attribs.samples);
-    }
-    if (init_params.attribs.stencil_size > 0) {
-      surface_format.SetStencilBits(init_params.attribs.stencil_size);
-    }
-    // Currently, we can't separately control alpha channel for surfaces,
-    // it's generally enabled by default except for RGB565 and (on desktop)
-    // smaller-than-32bit formats.
-    //
-    // TODO(klausw): use init_params.attribs.alpha_size here if possible.
     if (!surface_format.IsCompatible(default_surface->GetFormat())) {
       DVLOG(1) << __FUNCTION__ << ": Hit the OwnOffscreenSurface path";
       use_virtualized_gl_context_ = false;