fix for GrFragmentProcessor isEqual in GrPipeline

BUG=skia:

Review URL: https://codereview.chromium.org/1273693003
diff --git a/include/gpu/GrStagedProcessor.h b/include/gpu/GrStagedProcessor.h
index 1702831..a9f23b4 100644
--- a/include/gpu/GrStagedProcessor.h
+++ b/include/gpu/GrStagedProcessor.h
@@ -25,7 +25,7 @@
     const GrFragmentProcessor* processor() const { return fProc.get(); }
 
     bool operator==(const GrStagedProcessor& that) const {
-        return this->processor() == that.processor();
+        return this->processor()->isEqual(*that.processor());
     }
 
     bool operator!=(const GrStagedProcessor& that) const { return !(*this == that); }