Coalesce async touch move events until the ack back from render

ipc/param_traits_log_macros.h

 // Copyright (c) 2012 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.
 
 #ifndef IPC_PARAM_TRAITS_LOG_MACROS_H_
 #define IPC_PARAM_TRAITS_LOG_MACROS_H_
 
 #include <string>
 
 // Null out all the macros that need nulling.
 #include "ipc/ipc_message_null_macros.h"
 
 // STRUCT declarations cause corresponding STRUCT_TRAITS declarations to occur.
 #undef IPC_STRUCT_BEGIN_WITH_PARENT
 #undef IPC_STRUCT_MEMBER
 #undef IPC_STRUCT_END
 #define IPC_STRUCT_BEGIN_WITH_PARENT(struct_name, parent) \
   IPC_STRUCT_TRAITS_BEGIN(struct_name)
 #define IPC_STRUCT_MEMBER(type, name, ...) IPC_STRUCT_TRAITS_MEMBER(name)
 #define IPC_STRUCT_END() IPC_STRUCT_TRAITS_END()
 
 // Set up so next include will generate log methods.
 #undef IPC_STRUCT_TRAITS_BEGIN
 #undef IPC_STRUCT_TRAITS_MEMBER
 #undef IPC_STRUCT_TRAITS_PARENT
 #undef IPC_STRUCT_TRAITS_END
 #define IPC_STRUCT_TRAITS_BEGIN(struct_name) \
   void ParamTraits<struct_name>::Log(const param_type& p, std::string* l) { \
     bool needs_comma = false; \
+    ALLOW_UNUSED_LOCAL(needs_comma); \
     l->append("(");
 #define IPC_STRUCT_TRAITS_MEMBER(name) \
     if (needs_comma) \
       l->append(", "); \
     LogParam(p.name, l); \
     needs_comma = true;
 #define IPC_STRUCT_TRAITS_PARENT(type) \
     if (needs_comma) \
       l->append(", "); \
       ParamTraits<type>::Log(p, l); \
       needs_comma = true;
 #define IPC_STRUCT_TRAITS_END() \
     l->append(")"); \
   }
 
 #undef IPC_ENUM_TRAITS_VALIDATE
 #define IPC_ENUM_TRAITS_VALIDATE(enum_name, validation_expression) \
   void ParamTraits<enum_name>::Log(const param_type& p, std::string* l) { \
     LogParam(static_cast<int>(p), l); \
   }
 
 #endif  // IPC_PARAM_TRAITS_LOG_MACROS_H_