Add a requiresVertexShader method to GrGLEffect

src/gpu/effects/GrSimpleTextureEffect.cpp

Index: src/gpu/effects/GrSimpleTextureEffect.cpp
diff --git a/src/gpu/effects/GrSimpleTextureEffect.cpp b/src/gpu/effects/GrSimpleTextureEffect.cpp
index ccf761ab946c96e8d1e5ab3dbe5d7e804aaf5eca..6f1651f8b6ba7e35a12925ec9277dd66fd37b6c2 100644
--- a/src/gpu/effects/GrSimpleTextureEffect.cpp
+++ b/src/gpu/effects/GrSimpleTextureEffect.cpp
@@ -24,6 +24,11 @@ public:
         }
     }
 
+    virtual bool requiresVertexShader(const GrDrawEffect& drawEffect) const {
+        const GrSimpleTextureEffect& ste = drawEffect.castEffect<GrSimpleTextureEffect>();

[bsalomon, 2013/09/06 14:10:03]

Maybe we should make defer this decision to the effect matrix

e.g.

return fEffectMatrix->requiresVertexShader();

[Chris Dalton, 2013/09/06 17:17:24]

Actually, the way this code works is that when the coords type is
'kCustom_CoordsType', GrGLSimpleTextureEffect skips the effect matrix altogether
and outputs varyings directly to the vertex shader.

fEffectMatrix can always work without a vertex shader, because if there isn't
one, we're guaranteed that there aren't explicit local coords (we only go
vertexless if position is the only attribute).

[bsalomon, 2013/09/06 17:37:17]

oh, right, makes sense

+        return GrEffect::kCustom_CoordsType == ste.coordsType();
+    }
+
     virtual void emitCode(GrGLShaderBuilder* builder,
                           const GrDrawEffect& drawEffect,
                           EffectKey key,