Add transfer buffer support.

src/gpu/gl/GrGLBufferImpl.cpp

Index: src/gpu/gl/GrGLBufferImpl.cpp
diff --git a/src/gpu/gl/GrGLBufferImpl.cpp b/src/gpu/gl/GrGLBufferImpl.cpp
index 6cbf4e0d0eca4dde0274b31c3624a203f972cd9e..06fd441899338a8a461d993a95446319af001a1b 100644
--- a/src/gpu/gl/GrGLBufferImpl.cpp
+++ b/src/gpu/gl/GrGLBufferImpl.cpp
@@ -65,7 +65,7 @@ void* GrGLBufferImpl::map(GrGLGpu* gpu) {
     if (0 == fDesc.fID) {
         fMapPtr = fCPUData;
     } else {
-        fMapPtr = gpu->mapBuffer(fDesc.fID, fBufferType, fDesc.fDynamic, fGLSizeInBytes,
+        fMapPtr = gpu->mapBuffer(fDesc.fID, fBufferType, fDesc.fUsage, fGLSizeInBytes,
                                  fDesc.fSizeInBytes);
         fGLSizeInBytes = fDesc.fSizeInBytes;
     }
@@ -97,7 +97,7 @@ bool GrGLBufferImpl::updateData(GrGLGpu* gpu, const void* src, size_t srcSizeInB
         memcpy(fCPUData, src, srcSizeInBytes);
         return true;
     }
-    gpu->bufferData(fDesc.fID, fBufferType, fDesc.fDynamic, fDesc.fSizeInBytes, src,
+    gpu->bufferData(fDesc.fID, fBufferType, fDesc.fUsage, fDesc.fSizeInBytes, src,
                     srcSizeInBytes);
 #if GR_GL_USE_BUFFER_DATA_NULL_HINT
     fGLSizeInBytes = fDesc.fSizeInBytes;
@@ -109,7 +109,8 @@ bool GrGLBufferImpl::updateData(GrGLGpu* gpu, const void* src, size_t srcSizeInB
 }
 
 void GrGLBufferImpl::validate() const {
-    SkASSERT(GR_GL_ARRAY_BUFFER == fBufferType || GR_GL_ELEMENT_ARRAY_BUFFER == fBufferType);
+    SkASSERT(GR_GL_ARRAY_BUFFER == fBufferType || GR_GL_ELEMENT_ARRAY_BUFFER == fBufferType ||
+             GR_GL_PIXEL_PACK_BUFFER == fBufferType || GR_GL_PIXEL_UNPACK_BUFFER == fBufferType);
     // The following assert isn't valid when the buffer has been abandoned:
     // SkASSERT((0 == fDesc.fID) == (fCPUData));
     SkASSERT(nullptr == fCPUData || 0 == fGLSizeInBytes);