Added an extra sync token field for extra command buffer identification.

gpu/command_buffer/common/sync_token.h

Index: gpu/command_buffer/common/sync_token.h
diff --git a/gpu/command_buffer/common/sync_token.h b/gpu/command_buffer/common/sync_token.h
index 11af396265ab488e9e27c04763f65977ad36eab0..14f725681ebc2a76d6b4e6d0978dbaae63eca8f0 100644
--- a/gpu/command_buffer/common/sync_token.h
+++ b/gpu/command_buffer/common/sync_token.h
@@ -26,6 +26,7 @@ struct GPU_EXPORT SyncToken {
   SyncToken()
       : verified_flush_(false),
         namespace_id_(CommandBufferNamespace::INVALID),
+        extra_data_field_(0),
         command_buffer_id_(0),
         release_count_(0) {}
 
@@ -36,21 +37,26 @@ struct GPU_EXPORT SyncToken {
       : verified_flush_(sync_point ? true : false),
         namespace_id_(sync_point ? gpu::CommandBufferNamespace::OLD_SYNC_POINTS
                                  : gpu::CommandBufferNamespace::INVALID),
+        extra_data_field_(0),
         command_buffer_id_(0),
         release_count_(sync_point) {}
 
   SyncToken(CommandBufferNamespace namespace_id,
+            int32_t extra_data_field,
             uint64_t command_buffer_id,
             uint64_t release_count)
       : verified_flush_(false),
         namespace_id_(namespace_id),
+        extra_data_field_(extra_data_field),
         command_buffer_id_(command_buffer_id),
         release_count_(release_count) {}
 
   void Set(CommandBufferNamespace namespace_id,
+           int32_t extra_data_field,
            uint64_t command_buffer_id,
            uint64_t release_count) {
     namespace_id_ = namespace_id;
+    extra_data_field_ = extra_data_field;
     command_buffer_id_ = command_buffer_id;
     release_count_ = release_count;
   }
@@ -58,6 +64,7 @@ struct GPU_EXPORT SyncToken {
   void Clear() {
     verified_flush_ = false;
     namespace_id_ = CommandBufferNamespace::INVALID;
+    extra_data_field_ = 0;
     command_buffer_id_ = 0;
     release_count_ = 0;
   }
@@ -81,6 +88,12 @@ struct GPU_EXPORT SyncToken {
   uint64_t command_buffer_id() const { return command_buffer_id_; }
   uint64_t release_count() const { return release_count_; }
 
+  // This extra data field can be used by command buffers to add extra
+  // information to identify unverified sync tokens. The current purpose
+  // of this field is only for unverified sync tokens which only exist within
+  // the same process so this information will not survive cross-process IPCs.
+  int32_t extra_data_field() const { return extra_data_field_; }
+
   bool operator<(const SyncToken& other) const {
     // TODO(dyen): Once all our compilers support c++11, we can replace this
     // long list of comparisons with std::tie().
@@ -94,6 +107,7 @@ struct GPU_EXPORT SyncToken {
   bool operator==(const SyncToken& other) const {
     return verified_flush_ == other.verified_flush() &&
            namespace_id_ == other.namespace_id() &&
+           extra_data_field_ == other.extra_data_field() &&
            command_buffer_id_ == other.command_buffer_id() &&
            release_count_ == other.release_count();
   }
@@ -103,6 +117,7 @@ struct GPU_EXPORT SyncToken {
  private:
   bool verified_flush_;
   CommandBufferNamespace namespace_id_;
+  int32_t extra_data_field_;
   uint64_t command_buffer_id_;
   uint64_t release_count_;
 };