Make TestForPreservingPMConversions helper use lazy createTextureProxy call.

Bug: skia:
Change-Id: I337efc531aa5685c138b2f9e2bd47b47ba4e1fd5
Reviewed-on: https://skia-review.googlesource.com/114583
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
2 files changed