Always mark bitmap glyph runs as such, to ensure they are properly regenerated

If all glyphs were culled (by being too small), we could end up with a
run that never called setHasBitmap. That would prevent us from looking
at the view matrix on a subsequent draw, when deciding if we needed to
regenerate.

Bug: skia:8955
Change-Id: Ic7a2539762527f91bdb50ab78bdf5801bfda0034
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/206266
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>

gm/skbug_8955.cpp

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2019 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+
+#include "SkFont.h"
+#include "SkPaint.h"
+#include "SkTextBlob.h"
+
+DEF_SIMPLE_GM(skbug_8955, canvas, 100, 100) {
+    SkPaint p;
+    SkFont font;
+    font.setSize(50);
+    auto blob = SkTextBlob::MakeFromText("+", 1, font);
+
+    // This bug only appeared when drawing the same text blob. We would generate no glyphs on the
+    // first draw, and fail to mark the blob as having any bitmap runs. That would prevent us from
+    // re-generating the blob on the second draw, even though the matrix had been restored.
+    canvas->save();
+    canvas->scale(0, 0);
+    canvas->drawTextBlob(blob, 30, 60, p);
+    canvas->restore();
+    canvas->drawTextBlob(blob, 30, 60, p);
+}

gn/gm.gni

@@ -309,6 +309,7 @@ gm_sources = [
   "$_gm/skbug_4868.cpp",
   "$_gm/skbug_5321.cpp",
   "$_gm/skbug_8664.cpp",
+  "$_gm/skbug_8955.cpp",
   "$_gm/skbug1719.cpp",
   "$_gm/skinning.cpp",
   "$_gm/smallarc.cpp",

src/core/SkGlyphRunPainter.cpp

@@ -564,11 +564,11 @@ void SkGlyphRunListPainter::processGlyphRunList(const SkGlyphRunList& glyphRunLi
             }
 
             if (process) {
-                if (glyphsWithMaskCount > 0) {
-                    process->processDeviceMasks(
-                            SkSpan<const SkGlyphPos>{fGlyphPos, SkTo<size_t>(glyphsWithMaskCount)},
-                            strike.get());
-                }
+                // processDeviceMasks must be called even if there are no glyphs to make sure runs
+                // are set correctly.
+                process->processDeviceMasks(
+                        SkSpan<const SkGlyphPos>{fGlyphPos, SkTo<size_t>(glyphsWithMaskCount)},
+                        strike.get());
                 if (!fPaths.empty()) {
                     process->processDevicePaths(SkSpan<const SkGlyphPos>{fPaths});
                 }