Move DstCopy on gpu into the GrXferProcessor.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/74a11753604768bf461b80cabb66060e8564d82c

Review URL: https://codereview.chromium.org/885923002
diff --git a/src/gpu/GrPipelineBuilder.cpp b/src/gpu/GrPipelineBuilder.cpp
index 90aee74..54d357f 100644
--- a/src/gpu/GrPipelineBuilder.cpp
+++ b/src/gpu/GrPipelineBuilder.cpp
@@ -101,8 +101,8 @@
 
 //////////////////////////////////////////////////////////////////////////////s
 
-bool GrPipelineBuilder::willEffectReadDstColor() const {
-    return this->getXPFactory()->willReadDst();
+bool GrPipelineBuilder::willXPNeedDstCopy(const GrDrawTargetCaps& caps) const {
+    return this->getXPFactory()->willNeedDstCopy(caps);
 }
 
 void GrPipelineBuilder::AutoRestoreEffects::set(GrPipelineBuilder* pipelineBuilder) {