Remove hasMixedSamples() from GrPipelineBuilder

This info is unknown until after any clip has been applied to the
stencil settings, so it's misleading to include in the builder.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1952323002

Review-Url: https://codereview.chromium.org/1952323002
diff --git a/tools/debugger/SkOverdrawMode.cpp b/tools/debugger/SkOverdrawMode.cpp
index 1e018ba..bbf61cc 100644
--- a/tools/debugger/SkOverdrawMode.cpp
+++ b/tools/debugger/SkOverdrawMode.cpp
@@ -229,9 +229,7 @@
         return new OverdrawXP(dstTexture, hasMixedSamples);
     }
 
-    bool onWillReadDstColor(const GrCaps& caps,
-                            const GrPipelineOptimizations& optimizations,
-                            bool hasMixedSamples) const override {
+    bool onWillReadDstColor(const GrCaps&, const GrPipelineOptimizations&) const override {
         return true;
     }