Update from https://crrev.com/318214

tools/clang/blink_gc_plugin/Config.h

 // Copyright 2014 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.
 
 // This file defines the names used by GC infrastructure.
 
 // TODO: Restructure the name determination to use fully qualified names (ala,
 // blink::Foo) so that the plugin can be enabled for all of chromium. Doing so
 // would allow us to catch errors with structures outside of blink that might
 // have unsafe pointers to GC allocated blink structures.
 
 #ifndef TOOLS_BLINK_GC_PLUGIN_CONFIG_H_
 #define TOOLS_BLINK_GC_PLUGIN_CONFIG_H_
 
+#include <cassert>
+
 #include "clang/AST/AST.h"
 #include "clang/AST/Attr.h"
 
 const char kNewOperatorName[] = "operator new";
 const char kCreateName[] = "create";
 const char kTraceName[] = "trace";
 const char kTraceImplName[] = "traceImpl";
 const char kFinalizeName[] = "finalizeGarbageCollectedObject";
 const char kTraceAfterDispatchName[] = "traceAfterDispatch";
+const char kTraceAfterDispatchImplName[] = "traceAfterDispatchImpl";
 const char kRegisterWeakMembersName[] = "registerWeakMembers";
 const char kHeapAllocatorName[] = "HeapAllocator";
 const char kTraceIfNeededName[] = "TraceIfNeeded";
 const char kVisitorDispatcherName[] = "VisitorDispatcher";
+const char kVisitorVarName[] = "visitor";
 const char kAdjustAndMarkName[] = "adjustAndMark";
 const char kIsHeapObjectAliveName[] = "isHeapObjectAlive";
 
 class Config {
  public:
   static bool IsMember(const std::string& name) {
     return name == "Member";
   }
 
   static bool IsWeakMember(const std::string& name) {
@@ skipping 157 matching lines @@
                        formal_type.getTypePtr())) {
       if (parm_type->getDecl()->getName() == kVisitorDispatcherName) {
         // Unresolved, but its parameter name is VisitorDispatcher.
         return true;
       }
     }
 
     return IsVisitorPtrType(formal_type);
   }
 
-  static bool IsTraceMethod(clang::FunctionDecl* method,
-                            bool* is_trace_after_dispatch) {
+  enum TraceMethodType {
+    NOT_TRACE_METHOD,
+    TRACE_METHOD,
+    TRACE_AFTER_DISPATCH_METHOD,
+    TRACE_IMPL_METHOD,
+    TRACE_AFTER_DISPATCH_IMPL_METHOD
+  };
+
+  static TraceMethodType GetTraceMethodType(clang::FunctionDecl* method) {
     if (method->getNumParams() != 1)
-      return false;
+      return NOT_TRACE_METHOD;
 
     const std::string& name = method->getNameAsString();
     if (name != kTraceName && name != kTraceAfterDispatchName &&
-        name != kTraceImplName)
-      return false;
+        name != kTraceImplName && name != kTraceAfterDispatchImplName)
+      return NOT_TRACE_METHOD;
 
     const clang::QualType& formal_type = method->getParamDecl(0)->getType();
-    if (name == kTraceImplName) {
+    if (name == kTraceImplName || name == kTraceAfterDispatchImplName) {
       if (!IsVisitorDispatcherType(formal_type))
-        return false;
+        return NOT_TRACE_METHOD;
     } else if (!IsVisitorPtrType(formal_type)) {
-      return false;
+      return NOT_TRACE_METHOD;
     }
 
-    if (is_trace_after_dispatch)
-      *is_trace_after_dispatch = (name == kTraceAfterDispatchName);
+    if (name == kTraceName)
+      return TRACE_METHOD;
+    if (name == kTraceAfterDispatchName)
+      return TRACE_AFTER_DISPATCH_METHOD;
+    if (name == kTraceImplName)
+      return TRACE_AFTER_DISPATCH_METHOD;
+    if (name == kTraceAfterDispatchImplName)
+      return TRACE_AFTER_DISPATCH_IMPL_METHOD;
 
-    return true;
+    assert(false && "Should not reach here");
+    return NOT_TRACE_METHOD;
+  }
+
+  static bool IsTraceMethod(clang::FunctionDecl* method) {
+    return GetTraceMethodType(method) != NOT_TRACE_METHOD;
+  }
+
+  static bool IsTraceImplName(const std::string& name) {
+    return name == kTraceImplName || name == kTraceAfterDispatchImplName;
   }
 
   static bool StartsWith(const std::string& str, const std::string& prefix) {
     if (prefix.size() > str.size())
       return false;
     return str.compare(0, prefix.size(), prefix) == 0;
   }
 
   static bool EndsWith(const std::string& str, const std::string& suffix) {
     if (suffix.size() > str.size())
       return false;
     return str.compare(str.size() - suffix.size(), suffix.size(), suffix) == 0;
   }
 };
 
 #endif  // TOOLS_BLINK_GC_PLUGIN_CONFIG_H_