Compile all fiddle examples locally

Motivation: it would be a good idea if the API documentation examples
were checked into the skia repository, so we could make sure they
compile as part of the commit queue.

Fiddle would make/update a named fiddle each time it gets a new
commit of Skia, extracted from the code in the examples/ directory.
The docs would point at those named fiddles.  Named fiddles have urls
in the form:

    https://fiddle.skia.org/c/@Bitmap_000

Then we would stick a link to the example into the header documentation
like this:

    /** Allocates the pixel memory for the bitmap, given its dimensions
        and SkColorType. Returns true on success, where success means
        either setPixels() or setPixelRef() was called.

        @param bitmap  SkBitmap containing SkImageInfo as input, and
                       SkPixelRef as output
        @return        true if SkPixelRef was allocated

        @example       https://fiddle.skia.org/c/@Bitmap_000
    */
    bool allocPixelRef(SkBitmap* bitmap) override;

There are still around 200 disabled examples that need to be fixed
(these result from API changes since the author left).

Change-Id: I14a31348a9ccaaa31f65424b91e3a3533d2583a7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/198824
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
diff --git a/tools/fiddle/examples.cpp b/tools/fiddle/examples.cpp
new file mode 100644
index 0000000..d5cd067
--- /dev/null
+++ b/tools/fiddle/examples.cpp
@@ -0,0 +1,37 @@
+// Copyright 2019 Google LLC.
+// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
+
+#include "examples.h"
+
+template sk_tools::Registry<fiddle::Example>* sk_tools::Registry<fiddle::Example>::gHead;
+
+// These globals are needed by fiddles:
+GrBackendTexture backEndTexture;
+GrBackendRenderTarget backEndRenderTarget;
+GrBackendTexture backEndTextureRenderTarget;
+SkBitmap source;
+sk_sp<SkImage> image;
+double duration = 1.0;
+double frame = 1.0;
+
+int main() {
+    constexpr int kImgCount = 7;
+    sk_sp<SkImage> images[kImgCount];
+    SkBitmap bitmaps[kImgCount];
+    for (int i = 1; i < kImgCount; ++i) {
+        SkString path = SkStringPrintf("resources/images/example_%d.png", i);
+        images[i] = SkImage::MakeFromEncoded(SkData::MakeFromFileName(path.c_str()));
+        SkAssertResult(images[i] && images[i]->asLegacyBitmap(&bitmaps[i]));
+    }
+    for (const fiddle::Example& example : sk_tools::Registry<fiddle::Example>::Range()) {
+        SkASSERT((unsigned)example.fImageIndex < (unsigned)kImgCount);
+        image = images[example.fImageIndex];
+        source = bitmaps[example.fImageIndex];
+        SkBitmap bmp;
+        bmp.allocN32Pixels(example.fWidth, example.fHeight);
+        bmp.eraseColor(SK_ColorWHITE);
+        SkCanvas canvas(bmp);
+        SkDebugf("==> %s\n", example.fName);
+        example.fFunc(&canvas);
+    }
+}