Remove GP from drawstate, revision of invariant output for GP

BUG=skia:

Review URL: https://codereview.chromium.org/791743003
diff --git a/src/gpu/effects/GrBitmapTextGeoProc.h b/src/gpu/effects/GrBitmapTextGeoProc.h
index ce235ae..ef86704 100644
--- a/src/gpu/effects/GrBitmapTextGeoProc.h
+++ b/src/gpu/effects/GrBitmapTextGeoProc.h
@@ -45,7 +45,7 @@
 
     virtual bool onIsEqual(const GrGeometryProcessor& other) const SK_OVERRIDE;
 
-    virtual void onComputeInvariantOutput(GrInvariantOutput* inout) const SK_OVERRIDE;
+    virtual void onGetInvariantOutputCoverage(GrInitInvariantOutput*) const SK_OVERRIDE;
 
     GrTextureAccess    fTextureAccess;
     const GrAttribute* fInPosition;