Implement texel buffers

src/gpu/gl/GrGLBuffer.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLBuffer_DEFINED
 #define GrGLBuffer_DEFINED
 
 #include "GrBuffer.h"
 #include "gl/GrGLTypes.h"
 
 class GrGLGpu;
 class GrGLCaps;
 
 class GrGLBuffer : public GrBuffer {
 public:
     static GrGLBuffer* Create(GrGLGpu*, size_t size, GrBufferType intendedType, GrAccessPattern,
                               const void* data = nullptr);
 
     ~GrGLBuffer() {
         // either release or abandon should have been called by the owner of this object.
         SkASSERT(0 == fBufferID);
     }
 
     GrGLuint bufferID() const { return fBufferID; }
     size_t baseOffset() const { return reinterpret_cast<size_t>(fCPUData); }
 
+    /**
+     * Returns the actual size of the underlying GL buffer object. In certain cases we may make this
+     * smaller than the size reported by GrBuffer.
+     */
+    size_t glSizeInBytes() const { return fGLSizeInBytes; }
+
+    void setHasAttachedToTexture() { fHasAttachedToTexture = true; }
+    bool hasAttachedToTexture() const { return fHasAttachedToTexture; }
+
 protected:
     GrGLBuffer(GrGLGpu*, size_t size, GrBufferType intendedType, GrAccessPattern, bool cpuBacked,
                const void* data);
 
     void onAbandon() override;
     void onRelease() override;
     void setMemoryBacking(SkTraceMemoryDump* traceMemoryDump,
                           const SkString& dumpName) const override;
 
 private:
     GrGLGpu* glGpu() const;
     const GrGLCaps& glCaps() const;
 
     void onMap() override;
     void onUnmap() override;
     bool onUpdateData(const void* src, size_t srcSizeInBytes) override;
 
 #ifdef SK_DEBUG
     void validate() const;
 #endif
 
     void*          fCPUData;
     GrBufferType   fIntendedType;
     GrGLuint       fBufferID;
     size_t         fSizeInBytes;
     GrGLenum       fUsage;
-    size_t         fGLSizeInBytes;     // In certain cases we make the size of the GL buffer object
-                                       // smaller or larger than the size in fDesc.
+    size_t         fGLSizeInBytes;
+    bool           fHasAttachedToTexture;
 
     typedef GrBuffer INHERITED;
 };
 
 #endif