Align clang-format with the Checkstyle hook for short functions.

The latter doesn't allow non-empty methods on a single line. This is
the same in both C++ and Java. Test CL: https://r.android.com/2507738

#codehealth

Test: repo upload on a file with a short non-empty class method
      in C++ and Java formatted on multiple lines by clang-format.
Test: repo upload on a file with a short empty class method
      in C++ and Java formatted on a single line by clang-format.
Bug: 123456789
Change-Id: I9795cd753f0f31be97652859f5bd8b5ce3427c55