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_004.cpp b/docs/examples/Matrix_004.cpp
new file mode 100644
index 0000000..ad8f1c5
--- /dev/null
+++ b/docs/examples/Matrix_004.cpp
@@ -0,0 +1,29 @@
+// 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=ba19b36df8cd78586f3dff54e2d4c093
+REG_FIDDLE(Matrix_004, 256, 256, true, 0) {
+void draw(SkCanvas* canvas) {
+    auto debugster = [](const char* prefix, const SkMatrix& matrix) -> void {
+        SkString typeMask;
+        typeMask += SkMatrix::kIdentity_Mask == matrix.getType() ? "kIdentity_Mask " : "";
+        typeMask += SkMatrix::kTranslate_Mask & matrix.getType() ? "kTranslate_Mask " : "";
+        typeMask += SkMatrix::kScale_Mask & matrix.getType() ? "kScale_Mask " : "";
+        typeMask += SkMatrix::kAffine_Mask & matrix.getType() ? "kAffine_Mask " : "";
+        typeMask += SkMatrix::kPerspective_Mask & matrix.getType() ? "kPerspective_Mask" : "";
+        SkDebugf("after %s: %s\n", prefix, typeMask.c_str());
+    };
+SkMatrix matrix;
+matrix.reset();
+debugster("reset", matrix);
+matrix.postTranslate(1, 0);
+debugster("postTranslate", matrix);
+matrix.postScale(2, 1);
+debugster("postScale", matrix);
+matrix.postRotate(45);
+debugster("postScale", matrix);
+SkPoint polys[][4] = {{{0, 0}, {0, 1}, {1, 1}, {1, 0}}, {{0, 0}, {0, 1}, {2, 1}, {1, 0}}};
+matrix.setPolyToPoly(polys[0], polys[1], 4);
+debugster("setPolyToPoly", matrix);
+}
+}  // END FIDDLE