Remove image decoder and encoder autoregistration

src/images/SkImageDecoder_astc.cpp

Index: src/images/SkImageDecoder_astc.cpp
diff --git a/src/images/SkImageDecoder_astc.cpp b/src/images/SkImageDecoder_astc.cpp
index 79e98047d6b214c59db963c7d26aa25253295a3e..3e950d7f0c0927f344c710ee44b537c547305485 100644
--- a/src/images/SkImageDecoder_astc.cpp
+++ b/src/images/SkImageDecoder_astc.cpp
@@ -4,10 +4,10 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
+#include "SkImageDecoder_astc.h"
 
 #include "SkEndian.h"
 #include "SkColorPriv.h"
-#include "SkImageDecoder.h"
 #include "SkScaledBitmapSampler.h"
 #include "SkStream.h"
 #include "SkStreamPriv.h"
@@ -176,34 +176,20 @@ bool SkASTCImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
     return true;
 }
 
-/////////////////////////////////////////////////////////////////////////////////////////
-DEFINE_DECODER_CREATOR(ASTCImageDecoder);
-/////////////////////////////////////////////////////////////////////////////////////////
-
-static bool is_astc(SkStreamRewindable* stream) {
+SkImageDecoder::Format SkDetectFormatASTCImageDecoder(SkStreamRewindable* stream) {
     // Read the ASTC header and make sure it's valid.
     uint32_t magic;
-    if (stream->read((void*)&magic, 4) != 4) {
-        return false;
+    if (stream->read((void*)&magic, 4) == 4) {
+        if (kASTCMagicNumber == SkEndian_SwapLE32(magic))
+            return SkImageDecoder::kASTC_Format;
     }
-
-    return kASTCMagicNumber == SkEndian_SwapLE32(magic);
+    return SkImageDecoder::kUnknown_Format;
 }
 
-static SkImageDecoder* sk_libastc_dfactory(SkStreamRewindable* stream) {
-    if (is_astc(stream)) {
+SkImageDecoder* SkCreateASTCImageDecoder(SkStreamRewindable* stream) {
+    if (SkDetectFormatASTCImageDecoder(stream) == SkImageDecoder::kASTC_Format) {
         return SkNEW(SkASTCImageDecoder);
     }
     return NULL;
 }
 
-static SkImageDecoder_DecodeReg gReg(sk_libastc_dfactory);
-
-static SkImageDecoder::Format get_format_astc(SkStreamRewindable* stream) {
-    if (is_astc(stream)) {
-        return SkImageDecoder::kASTC_Format;
-    }
-    return SkImageDecoder::kUnknown_Format;
-}
-
-static SkImageDecoder_FormatReg gFormatReg(get_format_astc);