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

content/common/gpu/client/command_buffer_proxy_impl.cc

Index: content/common/gpu/client/command_buffer_proxy_impl.cc
diff --git a/content/common/gpu/client/command_buffer_proxy_impl.cc b/content/common/gpu/client/command_buffer_proxy_impl.cc
index 47e20d149ee54a844113bcb7e88b61ea754ac15b..cd93be8acda7a1be21c9a1e44a7fe76712ff4fd1 100644
--- a/content/common/gpu/client/command_buffer_proxy_impl.cc
+++ b/content/common/gpu/client/command_buffer_proxy_impl.cc
@@ -449,7 +449,7 @@ int32_t CommandBufferProxyImpl::CreateImage(ClientBuffer buffer,
 
   if (image_fence_sync) {
     gpu::SyncToken sync_token(GetNamespaceID(), GetCommandBufferID(),
-                              image_fence_sync);
+                              GetExtraCommandBufferData(), image_fence_sync);
 
     // Force a synchronous IPC to validate sync token.
     channel_->ValidateFlushIDReachedServer(stream_id_, true);
@@ -519,6 +519,10 @@ uint64_t CommandBufferProxyImpl::GetCommandBufferID() const {
   return command_buffer_id_;
 }
 
+int32_t CommandBufferProxyImpl::GetExtraCommandBufferData() const {
+  return stream_id_;
+}
+
 uint64_t CommandBufferProxyImpl::GenerateFenceSyncRelease() {
   return next_fence_sync_release_++;
 }
@@ -577,8 +581,20 @@ bool CommandBufferProxyImpl::CanWaitUnverifiedSyncToken(
   // Can only wait on an unverified sync token if it is from the same channel.
   const uint64_t token_channel = sync_token->command_buffer_id() >> 32;
   const uint64_t channel = command_buffer_id_ >> 32;
-  return (sync_token->namespace_id() == gpu::CommandBufferNamespace::GPU_IO &&
-          token_channel == channel);
+  if (sync_token->namespace_id() != gpu::CommandBufferNamespace::GPU_IO ||
+      token_channel != channel) {
+    return false;
+  }
+
+  // If waiting on a different stream, flush pending commands on that stream.
+  const int32_t release_stream_id = sync_token->extra_data_field();
+  if (release_stream_id == 0)
+    return false;
+
+  if (release_stream_id != stream_id_)
+    channel_->FlushPendingStream(release_stream_id);
+
+  return true;
 }
 
 uint32 CommandBufferProxyImpl::InsertSyncPoint() {