Rationalize GrContext's Gr*Proxy getter naming

This CL replaces the entry points:

asDeferredSurface
asDeferredTexture
asDeferredRenderTarget

with:

GrSurfaceProxy* asSurfaceProxy
sk_sp<GrSurfaceProxy> asSurfaceProxyRef

GrTextureProxy* asTextureProxy
sk_sp<GrTextureProxy> asTextureProxyRef

GrRenderTargetProxy* asRenderTargetProxy
sk_sp<GrRenderTargetProxy> asRenderTargetProxyRef

Change-Id: I7c2b1ea3d702023ff23019815ca13c9ff6f3b32d
Reviewed-on: https://skia-review.googlesource.com/7741
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/effects/SkDisplacementMapEffect.cpp b/src/effects/SkDisplacementMapEffect.cpp
index cee47f4..9693191 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -374,7 +374,7 @@
                                             context,
                                             SkIRect::MakeWH(bounds.width(), bounds.height()),
                                             kNeedNewImageUniqueID_SpecialImage,
-                                            sk_ref_sp(renderTargetContext->asDeferredTexture()),
+                                            renderTargetContext->asTextureProxyRef(),
                                             renderTargetContext->refColorSpace());
     }
 #endif