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/GrMagnifierEffect.cpp b/src/gpu/effects/generated/GrMagnifierEffect.cpp
index 722423a..5a29834 100644
--- a/src/gpu/effects/generated/GrMagnifierEffect.cpp
+++ b/src/gpu/effects/generated/GrMagnifierEffect.cpp
@@ -69,7 +69,10 @@
                 "d.y), 1.0);\n}\n%s = sample(%s, mix(coord, zoom_coord, weight)).%s;\n",
                 args.fOutputColor,
                 fragBuilder->getProgramBuilder()->samplerVariable(args.fTexSamplers[0]),
-                fragBuilder->getProgramBuilder()->samplerSwizzle(args.fTexSamplers[0]).c_str());
+                fragBuilder->getProgramBuilder()
+                        ->samplerSwizzle(args.fTexSamplers[0])
+                        .asString()
+                        .c_str());
     }
 
 private: