gpu: Fix a bug in the new ReturnFrontBuffer() path for pepper.

gpu/command_buffer/tests/gl_manager.h

Index: gpu/command_buffer/tests/gl_manager.h
diff --git a/gpu/command_buffer/tests/gl_manager.h b/gpu/command_buffer/tests/gl_manager.h
index a14cffec480580b347e005432773c9f89c1bd139..c24c6881f1e096fab04c5bc46308804b1dd287f2 100644
--- a/gpu/command_buffer/tests/gl_manager.h
+++ b/gpu/command_buffer/tests/gl_manager.h
@@ -75,6 +75,8 @@ class GLManager : private GpuControl {
     gles2::ContextType context_type;
     // Force shader name hashing for all context types.
     bool force_shader_name_hashing;
+    // Whether the buffer is multisampled.
+    bool multisampled;
   };
   GLManager();
   ~GLManager() override;