Add transfer buffer to GLCaps

src/gpu/gl/GrGLCaps.cpp

Index: src/gpu/gl/GrGLCaps.cpp
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index a768b371059fbc776c8fee9a17c8dc1d73788ffb..6c0ee19584c22775817176b4eb871261c7f62ec7 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -23,6 +23,7 @@ GrGLCaps::GrGLCaps(const GrContextOptions& contextOptions,
     fInvalidateFBType = kNone_InvalidateFBType;
     fLATCAlias = kLATC_LATCAlias;
     fMapBufferType = kNone_MapBufferType;
+    fTransferBufferType = kNone_TransferBufferType;
     fMaxFragmentUniformVectors = 0;
     fMaxVertexAttributes = 0;
     fMaxFragmentTextureUnits = 0;
@@ -370,6 +371,18 @@ void GrGLCaps::init(const GrContextOptions& contextOptions,
         }
     }
 
+    if (kGL_GrGLStandard == standard) {
+        if (version >= GR_GL_VER(3, 0) || ctxInfo.hasExtension("GL_ARB_pixel_buffer_object")) {
+            fTransferBufferType = kPBO_TransferBufferType;
+        } 
+    } else {
+        if (version >= GR_GL_VER(3, 0) || ctxInfo.hasExtension("GL_NV_pixel_buffer_object")) {
+            fTransferBufferType = kPBO_TransferBufferType;
+        } else if (ctxInfo.hasExtension("GL_CHROMIUM_pixel_transfer_buffer_object")) {
+            fTransferBufferType = kChromium_TransferBufferType;
+        }
+    }
+
     // On many GPUs, map memory is very expensive, so we effectively disable it here by setting the
     // threshold to the maximum unless the client gives us a hint that map memory is cheap.
     if (fGeometryBufferMapThreshold < 0) {