PPO: Fix updating sampler uniforms between draws Updating sampler uniforms when using PPOs is currently broken, since the Context/State use the currently bound ProgramExecutable which belongs to the PPO, but the updates only happen to the Program's executable that the uniform belongs to. This change updates Program::updateSamplerUniform() to update any PPO ProgramExecutables with the updated texture information when a Program's sampler uniforms are updated, so the Context/State use the correct data. Bug: b/182409935 Test: ProgramPipelineTest31.SampleTextureAThenTextureB Test: SamplersTest31.SampleTextureAThenTextureB Change-Id: I3c4e156c6e0c781e706f321f0bd12baf484ff42a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2797951 Commit-Queue: Tim Van Patten <timvp@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>