add SkStubHeifDecoderAPI.h

This should let us build SkHeifCodec even without libheif.

I didn't look at libheif itself, so this stub may disagree
a bit with the actual interface... just flailed around until
it compiled and linked.

This turns on the stub in most of our internal builds.

Change-Id: I62ed4993198118b2a8217ec846d92ff637cc8ab9
Reviewed-on: https://skia-review.googlesource.com/62321
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

BUILD.gn

@@ -31,7 +31,7 @@ declare_args() {
   skia_use_piex = !is_win
   skia_use_zlib = true
   skia_use_metal = false
-  skia_use_libheif = false
+  skia_use_libheif = is_skia_dev_build
 
   skia_android_serial = ""
   skia_enable_discrete_gpu = true

src/codec/SkHeifCodec.h

@@ -15,7 +15,16 @@
 #include "SkImageInfo.h"
 #include "SkSwizzler.h"
 #include "SkStream.h"
-#include "HeifDecoderAPI.h"
+
+#if !defined(__has_include)
+    #define __has_include(x) 0
+#endif
+
+#if __has_include("HeifDecoderAPI.h")
+    #include "HeifDecoderAPI.h"
+#else
+    #include "SkStubHeifDecoderAPI.h"
+#endif
 
 class SkHeifCodec : public SkCodec {
 public:

src/codec/SkStubHeifDecoderAPI.h

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkStubHeifDecoderAPI_DEFINED
+#define SkStubHeifDecoderAPI_DEFINED
+
+// This stub implementation of HeifDecoderAPI.h lets us compile SkHeifCodec.cpp
+// even when libheif is not available.  It, of course, does nothing and fails to decode.
+
+#include <memory>
+#include <stddef.h>
+#include <stdint.h>
+using off64_t = int64_t;
+
+enum HeifColorFormat {
+    kHeifColorFormat_RGB565,
+    kHeifColorFormat_RGBA_8888,
+    kHeifColorFormat_BGRA_8888,
+};
+
+struct HeifStream {
+    virtual ~HeifStream() {}
+
+    virtual size_t read(void*, size_t) = 0;
+    virtual bool   rewind()            = 0;
+    virtual bool   seek(size_t)        = 0;
+    virtual bool   hasLength() const   = 0;
+    virtual size_t getLength() const   = 0;
+};
+
+struct HeifFrameInfo {
+    int mRotationAngle;
+    int mWidth;
+    int mHeight;
+    int mBytesPerPixel;
+
+    size_t                  mIccSize;
+    std::unique_ptr<char[]> mIccData;
+};
+
+struct HeifDecoder {
+    bool init(HeifStream* stream, HeifFrameInfo*) {
+        delete stream;
+        return false;
+    }
+
+    bool decode(HeifFrameInfo*) {
+        return false;
+    }
+
+    bool setOutputColor(HeifColorFormat) {
+        return false;
+    }
+
+    bool getScanline(uint8_t*) {
+        return false;
+    }
+
+    int skipScanlines(int) {
+        return 0;
+    }
+};
+
+static inline HeifDecoder* createHeifDecoder() { return new HeifDecoder; }
+
+#endif//SkStubHeifDecoderAPI_DEFINED