Fix more disabled MSVC warnings, base/ edition.

Mostly this fixes cases of "possible value truncation", usually by inserting
explicit typecasts.

BUG=81439
TEST=none

Review URL: https://codereview.chromium.org/596103002

Cr-Commit-Position: refs/heads/master@{#297723}

• base/debug/crash_logging.cc[diff]
• base/debug/trace_event_impl.cc[diff]
• base/debug/trace_event_synthetic_delay_unittest.cc[diff]
• base/file_version_info_win.cc[diff]
• base/file_version_info_win.h[diff]
• base/files/file_path_unittest.cc[diff]
• base/files/file_util.cc[diff]
• base/json/json_parser.cc[diff]
• base/logging.cc[diff]
• base/logging.h[diff]
• base/logging_win.cc[diff]
• base/metrics/field_trial_unittest.cc[diff]
• base/metrics/histogram.cc[diff]
• base/metrics/histogram_base.cc[diff]
• base/numerics/safe_math.h[diff]
• base/numerics/safe_math_impl.h[diff]
• base/process/kill_win.cc[diff]
• base/strings/string_number_conversions.cc[diff]
• base/strings/string_util.h[diff]
• base/strings/utf_string_conversion_utils.cc[diff]
• base/sync_socket_win.cc[diff]
• base/test/gtest_xml_util.cc[diff]
• base/test/launcher/test_results_tracker.cc[diff]
• base/test/trace_event_analyzer_unittest.cc[diff]
• base/threading/platform_thread_win.cc[diff]
• base/time/time.h[diff]
• base/time/time_win.cc[diff]
• base/time/time_win_unittest.cc[diff]
• base/win/scoped_process_information_unittest.cc[diff]