Update GrSwizzle to only store key and not string.

Change-Id: Ieaba188e620e5c1f1d423109e628b0ca78f3afe0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257394
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/effects/generated/GrRRectBlurEffect.cpp b/src/gpu/effects/generated/GrRRectBlurEffect.cpp
index 630c66c..35cf1fe 100644
--- a/src/gpu/effects/generated/GrRRectBlurEffect.cpp
+++ b/src/gpu/effects/generated/GrRRectBlurEffect.cpp
@@ -94,7 +94,10 @@
                 "sample(%s, float2(texCoord)).%s;\n",
                 args.fOutputColor, args.fInputColor,
                 fragBuilder->getProgramBuilder()->samplerVariable(args.fTexSamplers[0]),
-                fragBuilder->getProgramBuilder()->samplerSwizzle(args.fTexSamplers[0]).c_str());
+                fragBuilder->getProgramBuilder()
+                        ->samplerSwizzle(args.fTexSamplers[0])
+                        .asString()
+                        .c_str());
     }
 
 private: