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/Matrix_093.cpp b/docs/examples/Matrix_093.cpp
new file mode 100644
index 0000000..84914fb
--- /dev/null
+++ b/docs/examples/Matrix_093.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=fad6b92b21b1e1deeae61978cec2d232
+REG_FIDDLE(Matrix_093, 256, 256, false, 3) {
+void draw(SkCanvas* canvas) {
+    SkMatrix matrix;
+    const SkPoint center = { 128, 128 };
+    matrix.setScale(20, 25, center.fX, center.fY);
+    matrix.postRotate(75, center.fX, center.fY);
+    {
+       SkAutoCanvasRestore acr(canvas, true);
+       canvas->concat(matrix);
+       canvas->drawBitmap(source, 0, 0);
+    }
+    if (matrix.isFixedStepInX()) {
+       SkPaint paint;
+       paint.setAntiAlias(true);
+       SkVector step = matrix.fixedStepInX(128);
+       SkVector end = center + step;
+       canvas->drawLine(center, end, paint);
+       SkVector arrow = { step.fX + step.fY, step.fY - step.fX};
+       arrow = arrow * .25f;
+       canvas->drawLine(end, end - arrow, paint);
+       canvas->drawLine(end, {end.fX + arrow.fY, end.fY - arrow.fX}, paint);
+    }
+}
+}  // END FIDDLE