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/Bitmap_053.cpp b/docs/examples/Bitmap_053.cpp
new file mode 100644
index 0000000..b622ecf
--- /dev/null
+++ b/docs/examples/Bitmap_053.cpp
@@ -0,0 +1,32 @@
+// 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=1b2800d23c9ea249b45c2c21a34b6d14
+REG_FIDDLE(Bitmap_053, 256, 32, false, 0) {
+class TinyAllocator : public SkBitmap::Allocator {
+public:
+    bool allocPixelRef(SkBitmap* bitmap) override {
+        const SkImageInfo& info = bitmap->info();
+        if (info.height() * info.minRowBytes() > sizeof(storage)) {
+            return false;
+        }
+        sk_sp<SkPixelRef> pr = sk_sp<SkPixelRef>(
+                new SkPixelRef(info.width(), info.height(), storage, info.minRowBytes()));
+        bitmap->setPixelRef(std::move(pr), 0, 0);
+        return true;
+    }
+    char storage[16];
+};
+
+void draw(SkCanvas* canvas) {
+   TinyAllocator tinyAllocator;
+   SkBitmap bitmap;
+   bitmap.setInfo(SkImageInfo::MakeN32(2, 2, kOpaque_SkAlphaType));
+   if (bitmap.tryAllocPixels(&tinyAllocator)) {
+       bitmap.eraseColor(0xff55aa33);
+       bitmap.erase(0xffaa3355, SkIRect::MakeXYWH(1, 1, 1, 1));
+       canvas->scale(16, 16);
+       canvas->drawBitmap(bitmap, 0, 0);
+   }
+}
+}  // END FIDDLE