aura: Change shared context to be offscreen for arm

gpu/command_buffer/service/gles2_cmd_decoder.h

Index: gpu/command_buffer/service/gles2_cmd_decoder.h
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.h b/gpu/command_buffer/service/gles2_cmd_decoder.h
index 1d1277ba7eaa579f4cb8797244fbef5ef93041e6..69be3ed1360175a3c5b44fdbff58cccf36e54dd0 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.h
@@ -87,6 +87,9 @@ class GPU_EXPORT GLES2Decoder : public CommonDecoder {
   // Parameters:
   //  surface: the GL surface to render to.
   //  context: the GL context to render to.
+  //  offscreen: whether to make the context offscreen or not. When FBO 0 is
+  //      bound, offscreen contexts render to an internal buffer, onscreen ones
+  //      to the surface.
   //  size: the size if the GL context is offscreen.
   //  allowed_extensions: A string in the same format as
   //      glGetString(GL_EXTENSIONS) that lists the extensions this context
@@ -95,6 +98,7 @@ class GPU_EXPORT GLES2Decoder : public CommonDecoder {
   //   true if successful.
   virtual bool Initialize(const scoped_refptr<gfx::GLSurface>& surface,
                           const scoped_refptr<gfx::GLContext>& context,
+                          bool offscreen,
                           const gfx::Size& size,
                           const DisallowedFeatures& disallowed_features,
                           const char* allowed_extensions,