Separate core and images project.

SkImage calls functions on SkImageDecoder and SkImageEncoder. This
is desired behavior, and it is also desired to include SkImage as
a part of core. In order to keep core from depending on images,
update SkImageDecoder_empty.cpp to implement all of SkImageDecoder
and SkImageEncoder. This file will be built by chrome (in
https://codereview.chromium.org/15960015).

Move force_linking from SkImageDecoder.cpp to its own file. It must
be called to force linking with the image decoders if desired. Call
the function in tools that need it:
sk_image
render_pictures
render_pdfs
sk_hello
filter
bench_pictures
debugger

SkImageDecoder:
Derive from SkNoncopyable, instead of duplicating its
hiding of constructors.

skhello:
Return rather than trying to write a null SkData to the stream.

Revert "Hamfistedly removed core dependence on images"
(commit 0f05f682a90bc125323677abf3476e1027d174f5) and
"Move SkImage::encode to SkImage_Codec.cpp."
(commit 83e47a954d0bf65439f3d9c0c93213063dd70da3.)
These two commits were temporary fixes that this change
cleans up.

SkSnapshot.cpp:
Check for a NULL encoder returned by SkImageEncoder::Create.

BUG=https://code.google.com/p/skia/issues/detail?id=1275
R=djsollen@google.com, robertphillips@google.com

Review URL: https://codereview.chromium.org/15806010

git-svn-id: http://skia.googlecode.com/svn/trunk@9364 2bbb7eff-a529-9590-31e7-b0007b416f81

2 files changed, 35 insertions, 24 deletions

diff --git a/src/images/SkForceLinking.cpp b/src/images/SkForceLinking.cpp
new file mode 100644
index 0000000000..81dbf2eac8
--- /dev/null
+++ b/src/images/SkForceLinking.cpp
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkForceLinking.h"
+#include "SkImageDecoder.h"
+
+// This method is required to fool the linker into not discarding the pre-main
+// initialization and registration of the decoder classes. Passing true will
+// cause memory leaks.
+int SkForceLinking(bool doNotPassTrue) {
+    if (doNotPassTrue) {
+        SkASSERT(false);
+        CreateJPEGImageDecoder();
+        CreateWEBPImageDecoder();
+        CreateBMPImageDecoder();
+        CreateICOImageDecoder();
+        CreateWBMPImageDecoder();
+#if defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_WIN)
+        CreateDefaultDecoder();
+#endif
+        // Only link GIF and PNG on platforms that build them. See images.gyp
+#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_NACL)
+        CreateGIFImageDecoder();
+#endif
+#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN)
+        CreatePNGImageDecoder();
+#endif
+        return -1;
+    }
+    return 0;
+}
diff --git a/src/images/SkImageDecoder.cpp b/src/images/SkImageDecoder.cpp
index 52c43c83f1..5c078ce630 100644
--- a/src/images/SkImageDecoder.cpp
+++ b/src/images/SkImageDecoder.cpp
@@ -450,27 +450,3 @@ bool SkImageDecoder::DecodeStream(SkStream* stream, SkBitmap* bm,
     }
     return success;
 }
-
-/**
- *  This function leaks, but that is okay because it is not intended
- *  to be called. It is only here so that the linker will include the
- *  decoders.
- *  Make sure to keep it in sync with images.gyp, so only the encoders
- *  which are created on a platform are linked.
- */
-void force_linking();
-void force_linking() {
-    SkASSERT(false);
-    CreateJPEGImageDecoder();
-    CreateWEBPImageDecoder();
-    CreateBMPImageDecoder();
-    CreateICOImageDecoder();
-    CreateWBMPImageDecoder();
-    // Only link GIF and PNG on platforms that build them. See images.gyp
-#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN) && !defined(SK_BUILD_FOR_NACL)
-    CreateGIFImageDecoder();
-#endif
-#if !defined(SK_BUILD_FOR_MAC) && !defined(SK_BUILD_FOR_WIN)
-    CreatePNGImageDecoder();
-#endif
-}