GrSlug proposed API for serialization

I don't have serialization working yet, but I have enough of the
plumbing to sketch out an API. It seems simplistic, but notice it
requires access to the SkStrikeClient.

Change-Id: I29f046b62f20c635cee86f0666e8112ac3097f16
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/507837
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Herb Derby <herb@google.com>

include/private/chromium/GrSlug.h

@@ -15,6 +15,7 @@ class SkCanvas;
 class SkMatrix;
 class SkPaint;
 class SkTextBlob;
+class SkWriteBuffer;
 
 // You can use GrSlug to simulate drawTextBlob by defining the following at compile time.
 //    SK_EXPERIMENTAL_SIMULATE_DRAWGLYPHRUNLIST_WITH_SLUG
@@ -43,6 +44,9 @@ public:
     // Draw the GrSlug obeying the canvas's mapping and clipping.
     void draw(SkCanvas* canvas);
 
+    // Serialize the slug.
+    virtual void flatten(SkWriteBuffer&) const = 0;
+
     virtual SkRect sourceBounds() const = 0;
     virtual const SkPaint& paint() const = 0;
 };

include/private/chromium/SkChromeRemoteGlyphCache.h

@@ -15,6 +15,7 @@
 #include "include/core/SkRefCnt.h"
 #include "include/utils/SkNoDrawCanvas.h"
 
+class GrSlug;
 struct SkPackedGlyphID;
 class SkAutoDescriptor;
 class SkStrikeCache;
@@ -138,6 +139,10 @@ public:
     // corresponding typefaceID on the GPU.
     SK_SPI bool translateTypefaceID(SkAutoDescriptor* descriptor) const;
 
+    // Given a buffer, unflatten into a slug making sure to do the typefaceID translation from
+    // renderer to GPU. Returns nullptr if there was a problem.
+    sk_sp<GrSlug> makeSlugFromBuffer(SkReadBuffer& buffer) const;
+
 private:
     std::unique_ptr<SkStrikeClientImpl> fImpl;
 };

src/core/SkChromeRemoteGlyphCache.cpp

@@ -1185,3 +1185,6 @@ bool SkStrikeClient::translateTypefaceID(SkAutoDescriptor* descriptor) const {
     return fImpl->translateTypefaceID(descriptor);
 }
 
+#if SK_SUPPORT_GPU
+sk_sp<GrSlug> SkStrikeClient::makeSlugFromBuffer(SkReadBuffer& buffer) const { return nullptr; }
+#endif  // SK_SUPPORT_GPU

src/gpu/text/GrTextBlob.cpp

@@ -2592,6 +2592,7 @@ public:
                      const SkMatrixProvider& viewMatrix,
                      skgpu::v1::SurfaceDrawContext* sdc);
 
+    void flatten(SkWriteBuffer& buffer) const override;
     SkRect sourceBounds() const override { return fSourceBounds; }
     const SkPaint& paint() const override { return fPaint; }
 
@@ -3121,6 +3122,8 @@ void Slug::processSourceMasks(const SkZip<SkGlyphVariant, SkPoint>& accepted,
 
     add_multi_mask_format(addGlyphsWithSameFormat, accepted, std::move(strike));
 }
+
+void Slug::flatten(SkWriteBuffer& buffer) const { SK_ABORT("Not implemented."); }
 }  // namespace
 
 namespace skgpu::v1 {