Rename outputSwizzle->writeSwizzle.

It is also used for writes to surfaces other than fragment shader
output. e.g. clears.

Change-Id: Id1eb79be6d1a8aed936456bffa59dee32661cec8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/280344
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/GrProgramDesc.h b/src/gpu/GrProgramDesc.h
index 916d0fc..2fd7324 100644
--- a/src/gpu/GrProgramDesc.h
+++ b/src/gpu/GrProgramDesc.h
@@ -104,7 +104,7 @@
     // TODO: this should be removed and converted to just data added to the key
     struct KeyHeader {
         // Set to uniquely identify any swizzling of the shader's output color(s).
-        uint16_t fOutputSwizzle;
+        uint16_t fWriteSwizzle;
         uint8_t fColorFragmentProcessorCnt; // Can be packed into 4 bits if required.
         uint8_t fCoverageFragmentProcessorCnt;
         // Set to uniquely identify the rt's origin, or 0 if the shader does not require this info.