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/GrBitmapTextGeoProc.cpp b/src/gpu/effects/GrBitmapTextGeoProc.cpp
index cd2fe56..93b4a0f 100644
--- a/src/gpu/effects/GrBitmapTextGeoProc.cpp
+++ b/src/gpu/effects/GrBitmapTextGeoProc.cpp
@@ -31,7 +31,7 @@
 
         // compute numbers to be hardcoded to convert texture coordinates from int to float
         SkASSERT(cte.numTextureSamplers() == 1);
-        SkDEBUGCODE(GrTexture* atlas = cte.textureSampler(0).texture());
+        SkDEBUGCODE(GrTexture* atlas = cte.textureSampler(0).peekTexture());
         SkASSERT(atlas && SkIsPow2(atlas->width()) && SkIsPow2(atlas->height()));
 
         GrGLSLVertToFrag v(kVec2f_GrSLType);