Add signalSyncPoint to the WebGraphicsContext3D command buffer impls.

content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc

Index: content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
diff --git a/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc b/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
index 0f2fcb129737dcd41a1469805c3ce752b11e7b4b..1ed9cfce821eda9a8cc3f562c9c59114ef56fbf4 100644
--- a/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
+++ b/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
@@ -1625,6 +1625,18 @@ DELEGATE_TO_GL(shallowFlushCHROMIUM,ShallowFlushCHROMIUM);
 
 DELEGATE_TO_GL_1(waitSyncPoint, WaitSyncPointCHROMIUM, GLuint)
 
+static void SignalSyncPointCallback(
+    WebKit::WebGraphicsContext3D::WebGraphicsSyncPointCallback* callback) {
+  callback->onSyncPointReached();
+}
+
+void WebGraphicsContext3DCommandBufferImpl::signalSyncPoint(
+    unsigned sync_point,
+    WebGraphicsSyncPointCallback* callback) {
+  command_buffer_->SignalSyncPoint(
+      sync_point, base::Bind(&SignalSyncPointCallback, callback));
+}
+
 void WebGraphicsContext3DCommandBufferImpl::genMailboxCHROMIUM(
     WGC3Dbyte* name) {
   std::vector<gpu::Mailbox> names(1);