Revise system for checking for uninstantiated proxies

The new pattern is:
  we will "instantiate" pipelines at flush time
  at flush time we will only access the backing GrSurface by peeking

  If instantiation fails we should never try to access the GrSurfaces


Change-Id: I87f7ff41bd0e84d9ca3dbdd61d3361d3d4ceefd6
Reviewed-on: https://skia-review.googlesource.com/17932
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/effects/GrMatrixConvolutionEffect.cpp b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
index b3ea81a..776eff0 100644
--- a/src/gpu/effects/GrMatrixConvolutionEffect.cpp
+++ b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
@@ -130,7 +130,7 @@
 void GrGLMatrixConvolutionEffect::onSetData(const GrGLSLProgramDataManager& pdman,
                                             const GrFragmentProcessor& processor) {
     const GrMatrixConvolutionEffect& conv = processor.cast<GrMatrixConvolutionEffect>();
-    GrTexture* texture = conv.textureSampler(0).texture();
+    GrTexture* texture = conv.textureSampler(0).peekTexture();
 
     float imageIncrement[2];
     float ySign = texture->origin() == kTopLeft_GrSurfaceOrigin ? 1.0f : -1.0f;