Add InternalSurfaceFlag so we know if RenderTargetProxys and RenderTargets use GL FBO 0.

Bug: skia:7748
Change-Id: I2fda3cde12ccdef19fe06ff287a8024b58d28ef0
Reviewed-on: https://skia-review.googlesource.com/124048
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index 55257a7..93e21cb 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -156,6 +156,7 @@
   "$_src/gpu/GrRenderTarget.cpp",
   "$_src/gpu/GrRenderTargetPriv.h",
   "$_src/gpu/GrRenderTargetProxy.cpp",
+  "$_src/gpu/GrRenderTargetProxyPriv.h",
   "$_src/gpu/GrReducedClip.cpp",
   "$_src/gpu/GrReducedClip.h",
   "$_src/gpu/GrRenderTargetContext.cpp",