Implement texel buffers

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index c2dda0a222be2ef16a73b1d8cd4fc1f5c4b6543c..c8b5d70f1b1d12ee573ee682376a930598f75761 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -60,6 +60,8 @@ public:
     void bindTexture(int unitIdx, const GrTextureParams& params, bool dstConfigAllowsSRGB,
                      GrGLTexture* texture);
 
+    void bindTexelBuffer(int unitIdx, intptr_t offsetInBytes, GrPixelConfig, GrGLBuffer*);
+
     bool onGetReadPixelsInfo(GrSurface* srcSurface, int readWidth, int readHeight, size_t rowBytes,
                              GrPixelConfig readConfig, DrawPreference*,
                              ReadPixelTempDrawInfo*) override;
@@ -88,6 +90,9 @@ public:
     // If the caller wishes to bind an index buffer to a specific VAO, it can call glBind directly.
     GrGLenum bindBuffer(GrBufferType type, const GrGLBuffer*);
 
+    // Called by GrGLBuffer after its buffer object has been destroyed.
+    void notifyBufferReleased(const GrGLBuffer*);
+
     const GrGLContext* glContextForTesting() const override {
         return &this->glContext();
     }
@@ -206,6 +211,8 @@ private:
     // binds texture unit in GL
     void setTextureUnit(int unitIdx);
 
+    void setTextureSwizzle(int unitIdx, GrGLenum target, const GrGLenum swizzle[]);
+
     // Flushes state from GrPipeline to GL. Returns false if the state couldn't be set.
     bool flushGLState(const GrPipeline& pipeline, const GrPrimitiveProcessor& primProc);
 
@@ -498,6 +505,23 @@ private:
     TriState                    fHWSRGBFramebuffer;
     SkTArray<uint32_t, true>    fHWBoundTextureUniqueIDs;
 
+    struct BufferTexture {
+        BufferTexture() : fTextureID(0), fKnownBound(false),
+                          fAttachedBufferUniqueID(SK_InvalidUniqueID),
+                          fSwizzle(GrSwizzle::RGBA()) {}
+
+        GrGLuint        fTextureID;
+        bool            fKnownBound;
+        intptr_t        fOffsetInBytes;
+        GrPixelConfig   fTexelConfig;
+        size_t          fAttachedSizeInBytes;
+        uint32_t        fAttachedBufferUniqueID;
+        GrSwizzle       fSwizzle;
+    };
+
+    SkTArray<BufferTexture, true>   fHWBufferTextures;
+    int                             fHWMaxUsedBufferTextureUnit;
+
     // EXT_raster_multisample.
     TriState                    fHWRasterMultisampleEnabled;
     int                         fHWNumRasterSamples;