Add higher resolution input for VEAUnittest running on Mac

When kVTVideoEncoderSpecification_RequireHardwareAcceleratedVideoEncoder is set,
VideoToolbox doesn't create encoder sessions below 640x384 resolution. From the
spec, this indicates that it is falling to SW implementation. Since we want to
actually test HW backed cases, we should input a higher resolution video for
Mac.

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel
Change-Id: Ie10cd533473ffca501f80772fffe27644004e123
Reviewed-on: https://chromium-review.googlesource.com/1019733
Commit-Queue: Emircan Uysaler <emircan@chromium.org>
Reviewed-by: Kuang-che Wu <kcwu@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553681}

media/gpu/video_encode_accelerator_unittest.cc

@@ -136,15 +136,21 @@ const unsigned int kFlushTimeoutMs = 2000;
 // - |requested_subsequent_framerate| framerate to switch to in the middle
 //                                    of the stream.
 //   Bitrate is only forced for tests that test bitrate.
-const char* g_default_in_filename = "bear_320x192_40frames.yuv";
 
 #if defined(OS_CHROMEOS) || defined(OS_LINUX)
+const char* g_default_in_filename = "bear_320x192_40frames.yuv";
 const base::FilePath::CharType* g_default_in_parameters =
     FILE_PATH_LITERAL(":320:192:1:out.h264:200000");
-#elif defined(OS_MACOSX) || defined(OS_WIN)
+#elif defined(OS_MACOSX)
+// VideoToolbox falls back to SW encoder with resolutions lower than this.
+const char* g_default_in_filename = "bear_640x384_40frames.yuv";
+const base::FilePath::CharType* g_default_in_parameters =
+    FILE_PATH_LITERAL(":640:384:1:out.h264:200000");
+#elif defined(OS_WIN)
+const char* g_default_in_filename = "bear_320x192_40frames.yuv";
 const base::FilePath::CharType* g_default_in_parameters =
     FILE_PATH_LITERAL(",320,192,0,out.h264,200000");
-#endif  // defined(OS_CHROMEOS)
+#endif  // defined(OS_CHROMEOS) || defined(OS_LINUX)
 
 // Default params that can be overriden via command line.
 std::unique_ptr<base::FilePath::StringType> g_test_stream_data(