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/tests/RenderTargetContextTest.cpp b/tests/RenderTargetContextTest.cpp
index 9a4b874..5917a2d 100644
--- a/tests/RenderTargetContextTest.cpp
+++ b/tests/RenderTargetContextTest.cpp
@@ -33,7 +33,7 @@
                                     bool wrappedExpectation) {
     REPORTER_ASSERT(reporter, rtCtx->isWrapped_ForTesting() == wrappedExpectation);
 
-    GrTextureProxy* tProxy = rtCtx->asDeferredTexture();
+    GrTextureProxy* tProxy = rtCtx->asTextureProxy();
     REPORTER_ASSERT(reporter, tProxy);
 
     REPORTER_ASSERT(reporter, tProxy->isWrapped_ForTesting() == wrappedExpectation);
@@ -68,7 +68,7 @@
 
         check_is_wrapped_status(reporter, rtCtx.get(), false);
 
-        GrTextureProxy* tProxy = rtCtx->asDeferredTexture();
+        GrTextureProxy* tProxy = rtCtx->asTextureProxy();
         REPORTER_ASSERT(reporter, tProxy);
 
         GrTexture* tex = tProxy->instantiate(ctx->textureProvider());