Fix IsGCMixin predicate to correctly identify classes with multiple mixin bases.

tools/clang/blink_gc_plugin/RecordInfo.cpp

 // 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.
 
 #include "Config.h"
 #include "RecordInfo.h"
 
 using namespace clang;
 using std::string;
 
@@ skipping 116 matching lines @@
     if (it->size() < 2) continue;
     const CXXBasePathElement& elem = (*it)[it->size() - 2];
     CXXRecordDecl* base = elem.Base->getType()->getAsCXXRecordDecl();
     if (Config::IsTreeSharedBase(base->getName()))
       return true;
   }
   return false;
 }
 
 // A GC mixin is a class that inherits from a GC mixin base and has
-// has not yet been "mixed in" with another GC base class.
+// not yet been "mixed in" with another GC base class.
 bool RecordInfo::IsGCMixin() {
   if (!IsGCDerived() || base_paths_->begin() == base_paths_->end())
     return false;
-  // Get the last element of the first path.
-  CXXBasePaths::paths_iterator it = base_paths_->begin();
-  const CXXBasePathElement& elem = (*it)[it->size() - 1];
-  CXXRecordDecl* base = elem.Base->getType()->getAsCXXRecordDecl();
-  // If it is not a mixin base we are done.
-  if (!Config::IsGCMixinBase(base->getName()))
-    return false;
-  // This is a mixin if there are no other paths to GC bases.
-  return ++it == base_paths_->end();
+  for (CXXBasePaths::paths_iterator it = base_paths_->begin();
+       it != base_paths_->end();
+       ++it) {
+      // Get the last element of the path.
+      const CXXBasePathElement& elem = (*it)[it->size() - 1];
+      CXXRecordDecl* base = elem.Base->getType()->getAsCXXRecordDecl();
+      // If it is not a mixin base we are done.
+      if (!Config::IsGCMixinBase(base->getName()))
+          return false;
+  }
+  // This is a mixin if all GC bases are mixins.
+  return true;
 }
 
 // Test if a record is allocated on the managed heap.
 bool RecordInfo::IsGCAllocated() {
   return IsGCDerived() || IsHeapAllocatedCollection();
 }
 
 RecordInfo* RecordCache::Lookup(CXXRecordDecl* record) {
   // Ignore classes annotated with the GC_PLUGIN_IGNORE macro.
   if (!record || Config::IsIgnoreAnnotated(record))
@@ skipping 345 matching lines @@
         // We failed to create an edge so abort the entire edge construction.
         delete edge;  // Will delete the already allocated members.
         return 0;
       }
     }
     return edge;
   }
 
   return new Value(info);
 }