hide SkBitmap::Config entirely (behind a flag)

patch from issue 339463002

TBR=

I think the NoGPU failure is unrelated, so ignoring
NOTRY=True

Author: reed@google.com

Review URL: https://codereview.chromium.org/340533002
diff --git a/tests/KtxTest.cpp b/tests/KtxTest.cpp
index 93edaf4..5cec2bf 100644
--- a/tests/KtxTest.cpp
+++ b/tests/KtxTest.cpp
@@ -62,7 +62,7 @@
     bool imageDecodeSuccess = SkImageDecoder::DecodeStream(stream, &decodedBitmap);
     REPORTER_ASSERT(reporter, imageDecodeSuccess);
 
-    REPORTER_ASSERT(reporter, decodedBitmap.config() == bm8888.config());
+    REPORTER_ASSERT(reporter, decodedBitmap.colorType() == bm8888.colorType());
     REPORTER_ASSERT(reporter, decodedBitmap.alphaType() == bm8888.alphaType());
     REPORTER_ASSERT(reporter, decodedBitmap.width() == bm8888.width());
     REPORTER_ASSERT(reporter, decodedBitmap.height() == bm8888.height());