Remove getter of writable GrEffectStage from GrDrawState.

Upcoming changes will require GrDrawState to know things about the set of installed effects. Thus all setting of effects must go through a GrDrawState function (setEffect()). This change accomplishes that.
Review URL: https://codereview.appspot.com/7214045

git-svn-id: http://skia.googlecode.com/svn/trunk@7411 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/effects/GrConfigConversionEffect.h b/src/gpu/effects/GrConfigConversionEffect.h
index 3845d32..169c3d7 100644
--- a/src/gpu/effects/GrConfigConversionEffect.h
+++ b/src/gpu/effects/GrConfigConversionEffect.h
@@ -35,11 +35,10 @@
     };
 
     // Installs an effect in the GrEffectStage to perform a config conversion.
-    static bool InstallEffect(GrTexture*,
-                              bool swapRedAndBlue,
-                              PMConversion pmConversion,
-                              const SkMatrix& matrix,
-                              GrEffectStage* stage);
+    static const GrEffectRef* Create(GrTexture*,
+                                     bool swapRedAndBlue,
+                                     PMConversion pmConversion,
+                                     const SkMatrix& matrix);
 
     static const char* Name() { return "Config Conversion"; }
     typedef GrGLConfigConversionEffect GLEffect;