Make mixed samples contingent on auxiliary extensions

src/gpu/gl/GrGLCaps.h

Index: src/gpu/gl/GrGLCaps.h
diff --git a/src/gpu/gl/GrGLCaps.h b/src/gpu/gl/GrGLCaps.h
index 663cd4be41a644e1cf9f0e75cb3f3b8aa808052e..5503576b2c0f4c3ed383f7e7f06522f4b33daa88 100644
--- a/src/gpu/gl/GrGLCaps.h
+++ b/src/gpu/gl/GrGLCaps.h
@@ -237,6 +237,9 @@ public:
     /// Is there support for ES2 compatability?
     bool ES2CompatibilitySupport() const { return fES2CompatibilitySupport; }
 
+    /// Can we call glDisable(GL_MULTISAMPLE)?
+    bool multisampleDisableSupport() const { return fMultisampleDisableSupport; }
+
     /// Use indices or vertices in CPU arrays rather than VBOs for dynamic content.
     bool useNonVBOVertexAndIndexDynamicData() const {
         return fUseNonVBOVertexAndIndexDynamicData;
@@ -353,6 +356,7 @@ private:
     bool fFragCoordsConventionSupport : 1;
     bool fVertexArrayObjectSupport : 1;
     bool fES2CompatibilitySupport : 1;
+    bool fMultisampleDisableSupport : 1;
     bool fUseNonVBOVertexAndIndexDynamicData : 1;
     bool fIsCoreProfile : 1;
     bool fFullClearIsFree : 1;