bug fix for glsl identity string

BUG=skia:

Review URL: https://codereview.chromium.org/659313004
diff --git a/src/gpu/gl/GrGLSL.cpp b/src/gpu/gl/GrGLSL.cpp
index 34c805e..d388d91 100644
--- a/src/gpu/gl/GrGLSL.cpp
+++ b/src/gpu/gl/GrGLSL.cpp
@@ -76,7 +76,11 @@
                 return "#version 300 es\n";
             } else {
                 SkASSERT(kGL_GrGLStandard == info.standard());
-                return "#version 330 compatibility\n";
+                if (info.caps()->isCoreProfile()) {
+                    return "#version 330\n";
+                } else {
+                    return "#version 330 compatibility\n";
+                }
             }
         case k310es_GrGLSLGeneration:
             SkASSERT(kGLES_GrGLStandard == info.standard());