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/docs/examples/Canvas_000.cpp b/docs/examples/Canvas_000.cpp
new file mode 100644
index 0000000..f11b0fd
--- /dev/null
+++ b/docs/examples/Canvas_000.cpp
@@ -0,0 +1,28 @@
+// 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 "fiddle/examples.h"
+// HASH=525285073aae7e53eb8f454a398f880c
+REG_FIDDLE(Canvas_000, 256, 256, true, 0) {
+void draw(SkCanvas* ) {
+    SkImageInfo info = SkImageInfo::MakeN32Premul(3, 3);  // device aligned, 32 bpp, Premultiplied
+    const size_t minRowBytes = info.minRowBytes();  // bytes used by one bitmap row
+    const size_t size = info.computeMinByteSize();  // bytes used by all rows
+    SkAutoTMalloc<SkPMColor> storage(size);  // allocate storage for pixels
+    SkPMColor* pixels = storage.get();  // get pointer to allocated storage
+    // create a SkCanvas backed by a raster device, and delete it when the
+    // function goes out of scope.
+    std::unique_ptr<SkCanvas> canvas = SkCanvas::MakeRasterDirect(info, pixels, minRowBytes);
+    canvas->clear(SK_ColorWHITE);  // white is Unpremultiplied, in ARGB order
+    canvas->flush();  // ensure that pixels are cleared
+    SkPMColor pmWhite = pixels[0];  // the Premultiplied format may vary
+    SkPaint paint;  // by default, draws black
+    canvas->drawPoint(1, 1, paint);  // draw in the center
+    canvas->flush();  // ensure that point was drawn
+    for (int y = 0; y < info.height(); ++y) {
+        for (int x = 0; x < info.width(); ++x) {
+            SkDebugf("%c", *pixels++ == pmWhite ? '-' : 'x');
+        }
+        SkDebugf("\n");
+    }
+}
+}  // END FIDDLE