fix for calling bindFragDataLocation on OpenGL 2.1

BUG=skia:3966

Review URL: https://codereview.chromium.org/1201623003
diff --git a/src/gpu/gl/GrGLCaps.h b/src/gpu/gl/GrGLCaps.h
index 1f5d6c2..3d33199 100644
--- a/src/gpu/gl/GrGLCaps.h
+++ b/src/gpu/gl/GrGLCaps.h
@@ -257,6 +257,8 @@
 
     bool fullClearIsFree() const { return fFullClearIsFree; }
 
+    bool bindFragDataLocationSupport() const { return fBindFragDataLocationSupport; }
+
     /**
      * Returns a string containing the caps info.
      */
@@ -367,6 +369,7 @@
     bool fUseNonVBOVertexAndIndexDynamicData : 1;
     bool fIsCoreProfile : 1;
     bool fFullClearIsFree : 1;
+    bool fBindFragDataLocationSupport : 1;
 
     struct ReadPixelsSupportedFormat {
         GrGLenum fFormat;