Edited Issue: Performance: InitializeDatabase regressed by changeset 1911dc7cef21 [1194]

[Changeset 1911dc7cef21db6e630b9258d53584a326438cc8](https://entityframework.codeplex.com/SourceControl/changeset/1911dc7cef21db6e630b9258d53584a326438cc8) introduces a performance regression to the database creation process of up to 22% (in very large models) when compared to previous versions of this same code.

The introduction of a new call to DbModelBuilder.Build() from GetDynamicUpdateModel led to this regression. From the profile of one of our tests, it’s clear that we are calling DbModelBuilder.Build() three times:

Call 1: LazyInternalContext.CreateModel.
Call 2: EdmxWriter.WriteEdmx.
Call 3: DbContextExtensions.GetDynamicUpdateModel.

This means that for a particular test, the three calls to DbModelBuilder.Build() represent 46.2% of the time spent loading the code first model.