Clean up SkSL operator utility functions

We had two copies of IsAssignment. Move everything into Compiler, with
consistent parameter names, etc...

Change-Id: Icc91da69075f4d20cac9b1a7328b717b05984b3f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/316223
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/src/sksl/SkSLByteCodeGenerator.cpp b/src/sksl/SkSLByteCodeGenerator.cpp
index bd274b9..6712336 100644
--- a/src/sksl/SkSLByteCodeGenerator.cpp
+++ b/src/sksl/SkSLByteCodeGenerator.cpp
@@ -696,10 +696,10 @@
                       rType.typeKind() == Type::TypeKind::kMatrix);
     Token::Kind op;
     std::unique_ptr<LValue> lvalue;
-    if (is_assignment(b.fOperator)) {
+    if (Compiler::IsAssignment(b.fOperator)) {
         lvalue = this->getLValue(*b.fLeft);
         lvalue->load();
-        op = remove_assignment(b.fOperator);
+        op = Compiler::RemoveAssignment(b.fOperator);
     } else {
         this->writeExpression(*b.fLeft);
         op = b.fOperator;