CC Animation: Use std::bitset to update animation state.

cc/animation/target_property.cc

 // Copyright (c) 2016 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 "cc/animation/target_property.h"
 
 #include "base/macros.h"
 
 namespace cc {
 
 namespace {
 
+static_assert(TargetProperty::FIRST_TARGET_PROPERTY == 0,
+              "TargetProperty must be 0-based enum");
+
 // This should match the TargetProperty enum.
 static const char* const s_targetPropertyNames[] = {
     "TRANSFORM", "OPACITY", "FILTER", "SCROLL_OFFSET", "BACKGROUND_COLOR"};
 
 static_assert(static_cast<int>(TargetProperty::LAST_TARGET_PROPERTY) + 1 ==
                   arraysize(s_targetPropertyNames),
               "TargetPropertyEnumSize should equal the number of elements in "
               "s_targetPropertyNames");
 
 }  // namespace
 
 const char* TargetProperty::GetName(TargetProperty::Type property) {
   return s_targetPropertyNames[property];
 }
 
 }  // namespace cc