Switch GetWallClockTime to using vectors for input and output.

Ensures that all converted timestamps will be monotonically increasing
within a single call to GetWallClockTime.

Performance seems unchanged (unit tests take the same amount of time).

As part of this change, also does the following:
- VideoRendererImpl unit test switched to WallClockTimeSource to avoid
having to reimplement the vector conversion routine.

BUG=485042
TEST=new unittest.

Review URL: https://codereview.chromium.org/1136513004

Cr-Commit-Position: refs/heads/master@{#329363}

• media/base/mock_filters.h[diff]
• media/base/time_source.h[diff]
• media/base/video_renderer.h[diff]
• media/base/wall_clock_time_source.cc[diff]
• media/base/wall_clock_time_source.h[diff]
• media/base/wall_clock_time_source_unittest.cc[diff]
• media/filters/video_renderer_algorithm.cc[diff]
• media/filters/video_renderer_algorithm.h[diff]
• media/filters/video_renderer_algorithm_unittest.cc[diff]
• media/renderers/audio_renderer_impl.cc[diff]
• media/renderers/audio_renderer_impl.h[diff]
• media/renderers/renderer_impl.cc[diff]
• media/renderers/renderer_impl.h[diff]
• media/renderers/video_renderer_impl.cc[diff]
• media/renderers/video_renderer_impl.h[diff]
• media/renderers/video_renderer_impl_unittest.cc[diff]