Add AVC level 5.2 to supported codecs

It appears that AVC level 5.2 is supported by Chrome for both encrypted and
non-encrypted videos, so update MIME checking to indicate that it is
supported.

BUG=622873
TEST=browser_tests pass

Change-Id: I569c1ec64313905ff38ae540c6bf354884959924
Reviewed-on: https://chromium-review.googlesource.com/c/1299909Reviewed-by: Chrome Cunningham <chcunningham@chromium.org>
Commit-Queue: John Rummell <jrummell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604414}

content/browser/media/media_canplaytype_browsertest.cc

@@ -1344,12 +1344,11 @@ IN_PROC_BROWSER_TEST_F(MediaCanPlayTypeTest, CodecSupportTest_AvcLevels) {
   EXPECT_EQ(kPropMaybe,    CanPlay("'video/mp4; codecs=\"avc1.42E041\"'"));
   EXPECT_EQ(kPropMaybe,    CanPlay("'video/mp4; codecs=\"avc1.42E042\"'"));
 
-  // Levels 5 (0x32), 5.1 (0x33).
-  // Note: Level 5.2 (0x34) is not considered valid (crbug.com/460376).
+  // Levels 5 (0x32), 5.1 (0x33), 5.2 (0x34).
   EXPECT_EQ(kPropMaybe,    CanPlay("'video/mp4; codecs=\"avc1.42E031\"'"));
   EXPECT_EQ(kPropProbably, CanPlay("'video/mp4; codecs=\"avc1.42E032\"'"));
   EXPECT_EQ(kPropProbably, CanPlay("'video/mp4; codecs=\"avc1.42E033\"'"));
-  EXPECT_EQ(kPropMaybe,    CanPlay("'video/mp4; codecs=\"avc1.42E034\"'"));
+  EXPECT_EQ(kPropProbably, CanPlay("'video/mp4; codecs=\"avc1.42E034\"'"));
   EXPECT_EQ(kPropMaybe,    CanPlay("'video/mp4; codecs=\"avc1.42E035\"'"));
   // Verify that decimal representations of levels are not supported.
   EXPECT_EQ(kPropMaybe,    CanPlay("'video/mp4; codecs=\"avc1.42E005\"'"));

media/base/mime_util_internal.cc

@@ -120,7 +120,7 @@ static bool IsValidH264Level(uint8_t level_idc) {
           (level_idc >= 20 && level_idc <= 22) ||
           (level_idc >= 30 && level_idc <= 32) ||
           (level_idc >= 40 && level_idc <= 42) ||
-          (level_idc >= 50 && level_idc <= 51));
+          (level_idc >= 50 && level_idc <= 52));
 }
 
 MimeUtil::MimeUtil() : allow_proprietary_codecs_(false) {