GC plugin: split out reporting of errors/warnings.

tools/clang/blink_gc_plugin/CheckFieldsVisitor.h

Index: tools/clang/blink_gc_plugin/CheckFieldsVisitor.h
diff --git a/tools/clang/blink_gc_plugin/CheckFieldsVisitor.h b/tools/clang/blink_gc_plugin/CheckFieldsVisitor.h
index d700be2ae0201fc78f49389721580da92daad116..4fddede3808738b04c3bb6f73ea03c43940ac7fb 100644
--- a/tools/clang/blink_gc_plugin/CheckFieldsVisitor.h
+++ b/tools/clang/blink_gc_plugin/CheckFieldsVisitor.h
@@ -31,9 +31,9 @@ class CheckFieldsVisitor : public RecursiveEdgeVisitor {
     kGCDerivedPartObject
   };
 
-  typedef std::vector<std::pair<FieldPoint*, Error> > Errors;
+  using Errors = std::vector<std::pair<FieldPoint*, Error>>;
 
-  explicit CheckFieldsVisitor(const BlinkGCPluginOptions& options);
+  CheckFieldsVisitor();
 
   Errors& invalid_fields();
 
@@ -46,7 +46,6 @@ class CheckFieldsVisitor : public RecursiveEdgeVisitor {
  private:
   Error InvalidSmartPtr(Edge* ptr);
 
-  const BlinkGCPluginOptions& options_;
   FieldPoint* current_;
   bool stack_allocated_host_;
   bool managed_host_;