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/src/gpu/gl/GrGLRenderTarget.cpp b/src/gpu/gl/GrGLRenderTarget.cpp
index 5513e8a..382457d 100644
--- a/src/gpu/gl/GrGLRenderTarget.cpp
+++ b/src/gpu/gl/GrGLRenderTarget.cpp
@@ -46,6 +46,9 @@
     if (glCaps.maxWindowRectangles() > 0 && idDesc.fRTFBOID) {
         this->setSupportsWindowRects();
     }
+    if (!idDesc.fRTFBOID) {
+        this->setGLRTFBOIDIs0();
+    }
 }
 
 void GrGLRenderTarget::init(const GrSurfaceDesc& desc, const IDDesc& idDesc) {