Merge commit for internal changes

diff --cc tensorflow/compiler/xla/service/BUILD
Simple merge

diff --cc tensorflow/contrib/cmake/tf_tests.cmake
Simple merge

diff --cc tensorflow/contrib/lite/examples/label_image/bitmap_helpers_impl.h
Simple merge

diff --cc tensorflow/core/kernels/depthwise_conv_op_gpu.cu.cc
Simple merge

diff --cc tensorflow/docs_src/get_started/get_started_for_beginners.md
Simple merge

diff --cc tensorflow/python/keras/_impl/keras/backend.py
Simple merge

diff --cc tensorflow/python/ops/math_grad.py
Simple merge

diff --cc tensorflow/tensorflow.bzl
Simple merge