Revert of GC plugin: improve error reporting when tracing illegal fields.

tools/clang/blink_gc_plugin/CheckFieldsVisitor.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "CheckFieldsVisitor.h"
 
 #include <cassert>
 
 #include "BlinkGCPluginOptions.h"
 #include "RecordInfo.h"
@@ skipping 68 matching lines @@
     invalid_fields_.push_back(std::make_pair(current_,
                                              kMemberToGCUnmanaged));
     return;
   }
 
   if (!Parent() || !edge->value()->IsGCAllocated())
     return;
 
   // Disallow  OwnPtr<T>, RefPtr<T> and T* to stack-allocated types.
   if (Parent()->IsOwnPtr() ||
-      Parent()->IsUniquePtr() ||
       Parent()->IsRefPtr() ||
       (stack_allocated_host_ && Parent()->IsRawPtr())) {
     invalid_fields_.push_back(std::make_pair(
         current_, InvalidSmartPtr(Parent())));
     return;
   }
   if (Parent()->IsRawPtr()) {
     RawPtr* rawPtr = static_cast<RawPtr*>(Parent());
     Error error = rawPtr->HasReferenceType() ?
         kReferencePtrToGCManaged : kRawPtrToGCManaged;
     invalid_fields_.push_back(std::make_pair(current_, error));
   }
 }
 
 void CheckFieldsVisitor::AtCollection(Collection* edge) {
   if (edge->on_heap() && Parent() && Parent()->IsOwnPtr())
     invalid_fields_.push_back(std::make_pair(current_, kOwnPtrToGCManaged));
-  if (edge->on_heap() && Parent() && Parent()->IsUniquePtr())
-    invalid_fields_.push_back(std::make_pair(current_, kUniquePtrToGCManaged));
 }
 
 CheckFieldsVisitor::Error CheckFieldsVisitor::InvalidSmartPtr(Edge* ptr) {
   if (ptr->IsRawPtr()) {
     if (static_cast<RawPtr*>(ptr)->HasReferenceType())
       return kReferencePtrToGCManaged;
     else
       return kRawPtrToGCManaged;
   }
   if (ptr->IsRefPtr())
     return kRefPtrToGCManaged;
   if (ptr->IsOwnPtr())
     return kOwnPtrToGCManaged;
-  if (ptr->IsUniquePtr())
-    return kUniquePtrToGCManaged;
   assert(false && "Unknown smart pointer kind");
 }