Add glClientWaitSync to GPU command buffer.

gpu/command_buffer/common/gles2_cmd_format.h

Index: gpu/command_buffer/common/gles2_cmd_format.h
diff --git a/gpu/command_buffer/common/gles2_cmd_format.h b/gpu/command_buffer/common/gles2_cmd_format.h
index 944edfd5d0c639a497b95107e9a8ff4f197da49a..9cde09ca78c4269d56bcd00349db88861f55cf4c 100644
--- a/gpu/command_buffer/common/gles2_cmd_format.h
+++ b/gpu/command_buffer/common/gles2_cmd_format.h
@@ -43,6 +43,7 @@ typedef void GLvoid;
 typedef khronos_intptr_t GLintptr;
 typedef khronos_ssize_t  GLsizeiptr;
 typedef struct __GLsync *GLsync;
+typedef uint64_t GLuint64;
 
 namespace gpu {
 namespace gles2 {
@@ -77,6 +78,19 @@ static_assert(kTextures == 4, "kTextures should equal 4");
 
 }  // namespace id_namespaces
 
+union GLuint64Union {
+  GLuint64 param64;
+  uint32_t param32[2];
+};
+
+static_assert(sizeof(GLuint64Union) == 8, "size of GLuint64Union should be 8");
+static_assert(offsetof(GLuint64Union, param64) == 0,
+              "offset of GLuint64Union.param64 should be 0");
+static_assert(offsetof(GLuint64Union, param32[0]) == 0,
+              "offset of GLuint64Union.param32[0] should be 0");
+static_assert(offsetof(GLuint64Union, param32[1]) == 4,
+              "offset of GLuint64Union.param32[1] should be 4");
+
 // Used for some glGetXXX commands that return a result through a pointer. We
 // need to know if the command succeeded or not and the size of the result. If
 // the command failed its result size will 0.