Merge third_party/icu from https://chromium.googlesource.com/chromium/deps/icu46.git at 7ca74f5fd2718465d49d53b08110e87dc7e46a5c

This commit was generated by merge_from_chromium.py.

Change-Id: I10e4b6ebe050fdef67dc06f55c8f27f2608a381f