Add glWaitSync to GPU command buffer.

gpu/command_buffer/client/gles2_implementation.cc

Index: gpu/command_buffer/client/gles2_implementation.cc
diff --git a/gpu/command_buffer/client/gles2_implementation.cc b/gpu/command_buffer/client/gles2_implementation.cc
index 338e09df48327c7611d66d9ea32ccd534207fb5e..2dd95ec410850613d8279ef3ba12b7d0bb884469 100644
--- a/gpu/command_buffer/client/gles2_implementation.cc
+++ b/gpu/command_buffer/client/gles2_implementation.cc
@@ -4953,6 +4953,17 @@ GLenum GLES2Implementation::ClientWaitSync(
   return *result;
 }
 
+void GLES2Implementation::WaitSync(
+    GLsync sync, GLbitfield flags, GLuint64 timeout) {
+  GPU_CLIENT_SINGLE_THREAD_CHECK();
+  GPU_CLIENT_LOG("[" << GetLogPrefix() << "] glWaitSync(" << sync << ", "
+                 << flags << ", " << timeout << ")");
+  uint32_t v32_0 = 0, v32_1 = 0;
+  GLES2Util::MapUint64ToTwoUint32(timeout, &v32_0, &v32_1);
+  helper_->WaitSync(ToGLuint(sync), flags, v32_0, v32_1);
+  CheckGLError();
+}
+
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.