Extracted media mime type checks from net/base/ into media/base/

media/base/mime_util.cc

Index: media/base/mime_util.cc
diff --git a/media/base/mime_util.cc b/media/base/mime_util.cc
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+++ b/media/base/mime_util.cc
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+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <algorithm>
+#include <iterator>
+#include <map>
+#include <string>
+
+#include "base/containers/hash_tables.h"
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/stl_util.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
+#include "media/base/mime_util.h"
+
+#if defined(OS_ANDROID)
+#include "base/android/build_info.h"
+#endif
+
+namespace media {
+
+// Singleton utility class for mime types.
+class MimeUtil {
+ public:
+  enum Codec {
+    INVALID_CODEC,
+    PCM,
+    MP3,
+    MPEG2_AAC_LC,
+    MPEG2_AAC_MAIN,
+    MPEG2_AAC_SSR,
+    MPEG4_AAC_LC,
+    MPEG4_AAC_SBR_v1,
+    MPEG4_AAC_SBR_PS_v2,
+    VORBIS,
+    OPUS,
+    H264_BASELINE,
+    H264_MAIN,
+    H264_HIGH,
+    VP8,
+    VP9,
+    THEORA
+  };
+
+  bool IsSupportedMediaMimeType(const std::string& mime_type) const;
+
+  bool AreSupportedMediaCodecs(const std::vector<std::string>& codecs) const;
+
+  void ParseCodecString(const std::string& codecs,
+                        std::vector<std::string>* codecs_out,
+                        bool strip);
+
+  bool IsStrictMediaMimeType(const std::string& mime_type) const;
+  SupportsType IsSupportedStrictMediaMimeType(
+      const std::string& mime_type,
+      const std::vector<std::string>& codecs) const;
+
+  void RemoveProprietaryMediaTypesAndCodecsForTests();
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<MimeUtil>;
+
+  typedef base::hash_set<std::string> MimeMappings;
+
+  typedef base::hash_set<int> CodecSet;
+  typedef std::map<std::string, CodecSet> StrictMappings;
+  struct CodecEntry {
+    CodecEntry() : codec(INVALID_CODEC), is_ambiguous(true) {}
+    CodecEntry(Codec c, bool ambiguous) : codec(c), is_ambiguous(ambiguous) {}
+    Codec codec;
+    bool is_ambiguous;
+  };
+  typedef std::map<std::string, CodecEntry> StringToCodecMappings;
+
+  MimeUtil();
+
+  // Returns IsSupported if all codec IDs in |codecs| are unambiguous
+  // and are supported by the platform. MayBeSupported is returned if
+  // at least one codec ID in |codecs| is ambiguous but all the codecs
+  // are supported by the platform. IsNotSupported is returned if at
+  // least one codec ID  is not supported by the platform.
+  SupportsType AreSupportedCodecs(
+      const CodecSet& supported_codecs,
+      const std::vector<std::string>& codecs) const;
+
+  // For faster lookup, keep hash sets.
+  void InitializeMimeTypeMaps();
+
+  // Converts a codec ID into an Codec enum value and indicates
+  // whether the conversion was ambiguous.
+  // Returns true if this method was able to map |codec_id| to a specific
+  // Codec enum value. |codec| and |is_ambiguous| are only valid if true
+  // is returned. Otherwise their value is undefined after the call.
+  // |is_ambiguous| is true if |codec_id| did not have enough information to
+  // unambiguously determine the proper Codec enum value. If |is_ambiguous|
+  // is true |codec| contains the best guess for the intended Codec enum value.
+  bool StringToCodec(const std::string& codec_id,
+                     Codec* codec,
+                     bool* is_ambiguous) const;
+
+  // Returns true if |codec| is supported by the platform.
+  // Note: This method will return false if the platform supports proprietary
+  // codecs but |allow_proprietary_codecs_| is set to false.
+  bool IsCodecSupported(Codec codec) const;
+
+  // Returns true if |codec| refers to a proprietary codec.
+  bool IsCodecProprietary(Codec codec) const;
+
+  // Returns true and sets |*default_codec| if |mime_type| has a  default codec
+  // associated with it. Returns false otherwise and the value of
+  // |*default_codec| is undefined.
+  bool GetDefaultCodecLowerCase(const std::string& mime_type_lower_case,
+                                Codec* default_codec) const;
+
+  // Returns true if |mime_type_lower_case| has a default codec associated with
+  // it and IsCodecSupported() returns true for that particular codec.
+  bool IsDefaultCodecSupportedLowerCase(
+      const std::string& mime_type_lower_case) const;
+
+  MimeMappings media_map_;
+
+  // A map of mime_types and hash map of the supported codecs for the mime_type.
+  StrictMappings strict_format_map_;
+
+  // Keeps track of whether proprietary codec support should be
+  // advertised to callers.
+  bool allow_proprietary_codecs_;
+
+  // Lookup table for string compare based string -> Codec mappings.
+  StringToCodecMappings string_to_codec_map_;
+};  // class MimeUtil
+
+// This variable is Leaky because we need to access it from WorkerPool threads.
+static base::LazyInstance<MimeUtil>::Leaky g_mime_util =
+    LAZY_INSTANCE_INITIALIZER;
+
+// A list of media types: http://en.wikipedia.org/wiki/Internet_media_type
+// A comprehensive mime type list: http://plugindoc.mozdev.org/winmime.php
+// This set of codecs is supported by all variations of Chromium.
+static const char* const common_media_types[] = {
+  // Ogg.
+  "audio/ogg",
+  "application/ogg",
+#if !defined(OS_ANDROID)  // Android doesn't support Ogg Theora.
+  "video/ogg",
+#endif
+
+  // WebM.
+  "video/webm",
+  "audio/webm",
+
+  // Wav.
+  "audio/wav",
+  "audio/x-wav",
+
+#if defined(OS_ANDROID)
+  // HLS. Supported by Android ICS and above.
+  "application/vnd.apple.mpegurl",
+  "application/x-mpegurl",
+#endif
+};
+
+// List of proprietary types only supported by Google Chrome.
+static const char* const proprietary_media_types[] = {
+  // MPEG-4.
+  "video/mp4",
+  "video/x-m4v",
+  "audio/mp4",
+  "audio/x-m4a",
+
+  // MP3.
+  "audio/mp3",
+  "audio/x-mp3",
+  "audio/mpeg",
+  "audio/aac",
+
+#if defined(ENABLE_MPEG2TS_STREAM_PARSER)
+  // MPEG-2 TS.
+  "video/mp2t",
+#endif
+};
+
+#if defined(OS_ANDROID)
+static bool IsCodecSupportedOnAndroid(MimeUtil::Codec codec) {
+  switch (codec) {
+    case MimeUtil::INVALID_CODEC:
+      return false;
+
+    case MimeUtil::PCM:
+    case MimeUtil::MP3:
+    case MimeUtil::MPEG4_AAC_LC:
+    case MimeUtil::MPEG4_AAC_SBR_v1:
+    case MimeUtil::MPEG4_AAC_SBR_PS_v2:
+    case MimeUtil::H264_BASELINE:
+    case MimeUtil::H264_MAIN:
+    case MimeUtil::H264_HIGH:
+    case MimeUtil::VP8:
+    case MimeUtil::VORBIS:
+      return true;
+
+    case MimeUtil::MPEG2_AAC_LC:
+    case MimeUtil::MPEG2_AAC_MAIN:
+    case MimeUtil::MPEG2_AAC_SSR:
+      // MPEG-2 variants of AAC are not supported on Android.
+      return false;
+
+    case MimeUtil::VP9:
+      // VP9 is supported only in KitKat+ (API Level 19).
+      return base::android::BuildInfo::GetInstance()->sdk_int() >= 19;
+
+    case MimeUtil::OPUS:
+      // Opus is supported only in Lollipop+ (API Level 21).
+      return base::android::BuildInfo::GetInstance()->sdk_int() >= 21;
+
+    case MimeUtil::THEORA:
+      return false;
+  }
+
+  return false;
+}
+
+static bool IsMimeTypeSupportedOnAndroid(const std::string& mimeType) {
+  // HLS codecs are supported in ICS and above (API level 14)
+  if ((!mimeType.compare("application/vnd.apple.mpegurl") ||
+      !mimeType.compare("application/x-mpegurl")) &&
+      base::android::BuildInfo::GetInstance()->sdk_int() < 14) {
+    return false;
+  }
+  return true;
+}
+#endif
+
+struct MediaFormatStrict {
+  const char* const mime_type;
+  const char* const codecs_list;
+};
+
+// Following is the list of RFC 6381 compliant codecs:
+//   mp4a.66     - MPEG-2 AAC MAIN
+//   mp4a.67     - MPEG-2 AAC LC
+//   mp4a.68     - MPEG-2 AAC SSR
+//   mp4a.69     - MPEG-2 extension to MPEG-1
+//   mp4a.6B     - MPEG-1 audio
+//   mp4a.40.2   - MPEG-4 AAC LC
+//   mp4a.40.02  - MPEG-4 AAC LC (leading 0 in aud-oti for compatibility)
+//   mp4a.40.5   - MPEG-4 HE-AAC v1 (AAC LC + SBR)
+//   mp4a.40.05  - MPEG-4 HE-AAC v1 (AAC LC + SBR) (leading 0 in aud-oti for
+//                 compatibility)
+//   mp4a.40.29  - MPEG-4 HE-AAC v2 (AAC LC + SBR + PS)
+//
+//   avc1.42E0xx - H.264 Baseline
+//   avc1.4D40xx - H.264 Main
+//   avc1.6400xx - H.264 High
+static const char kMP4AudioCodecsExpression[] =
+    "mp4a.66,mp4a.67,mp4a.68,mp4a.69,mp4a.6B,mp4a.40.2,mp4a.40.02,mp4a.40.5,"
+    "mp4a.40.05,mp4a.40.29";
+static const char kMP4VideoCodecsExpression[] =
+    // This is not a complete list of supported avc1 codecs. It is simply used
+    // to register support for the corresponding Codec enum. Instead of using
+    // strings in these three arrays, we should use the Codec enum values.
+    // This will avoid confusion and unnecessary parsing at runtime.
+    // kUnambiguousCodecStringMap/kAmbiguousCodecStringMap should be the only
+    // mapping from strings to codecs. See crbug.com/461009.
+    "avc1.42E00A,avc1.4D400A,avc1.64000A,"
+    "mp4a.66,mp4a.67,mp4a.68,mp4a.69,mp4a.6B,mp4a.40.2,mp4a.40.02,mp4a.40.5,"
+    "mp4a.40.05,mp4a.40.29";
+
+// These containers are also included in
+// common_media_types/proprietary_media_types. See crbug.com/461012.
+static const MediaFormatStrict format_codec_mappings[] = {
+    {"video/webm", "opus,vorbis,vp8,vp8.0,vp9,vp9.0"},
+    {"audio/webm", "opus,vorbis"},
+    {"audio/wav", "1"},
+    {"audio/x-wav", "1"},
+// Android does not support Opus in Ogg container.
+#if defined(OS_ANDROID)
+    {"video/ogg", "theora,vorbis"},
+    {"audio/ogg", "vorbis"},
+    {"application/ogg", "theora,vorbis"},
+#else
+    {"video/ogg", "opus,theora,vorbis"},
+    {"audio/ogg", "opus,vorbis"},
+    {"application/ogg", "opus,theora,vorbis"},
+#endif
+    {"audio/mpeg", "mp3"},
+    {"audio/mp3", ""},
+    {"audio/x-mp3", ""},
+    {"audio/mp4", kMP4AudioCodecsExpression},
+    {"audio/x-m4a", kMP4AudioCodecsExpression},
+    {"video/mp4", kMP4VideoCodecsExpression},
+    {"video/x-m4v", kMP4VideoCodecsExpression},
+    {"application/x-mpegurl", kMP4VideoCodecsExpression},
+    {"application/vnd.apple.mpegurl", kMP4VideoCodecsExpression}};
+
+struct CodecIDMappings {
+  const char* const codec_id;
+  MimeUtil::Codec codec;
+};
+
+// List of codec IDs that provide enough information to determine the
+// codec and profile being requested.
+//
+// The "mp4a" strings come from RFC 6381.
+static const CodecIDMappings kUnambiguousCodecStringMap[] = {
+    {"1", MimeUtil::PCM},  // We only allow this for WAV so it isn't ambiguous.
+    // avc1/avc3.XXXXXX may be unambiguous; handled by ParseH264CodecID().
+    {"mp3", MimeUtil::MP3},
+    {"mp4a.66", MimeUtil::MPEG2_AAC_MAIN},
+    {"mp4a.67", MimeUtil::MPEG2_AAC_LC},
+    {"mp4a.68", MimeUtil::MPEG2_AAC_SSR},
+    {"mp4a.69", MimeUtil::MP3},
+    {"mp4a.6B", MimeUtil::MP3},
+    {"mp4a.40.2", MimeUtil::MPEG4_AAC_LC},
+    {"mp4a.40.02", MimeUtil::MPEG4_AAC_LC},
+    {"mp4a.40.5", MimeUtil::MPEG4_AAC_SBR_v1},
+    {"mp4a.40.05", MimeUtil::MPEG4_AAC_SBR_v1},
+    {"mp4a.40.29", MimeUtil::MPEG4_AAC_SBR_PS_v2},
+    {"vorbis", MimeUtil::VORBIS},
+    {"opus", MimeUtil::OPUS},
+    {"vp8", MimeUtil::VP8},
+    {"vp8.0", MimeUtil::VP8},
+    {"vp9", MimeUtil::VP9},
+    {"vp9.0", MimeUtil::VP9},
+    {"theora", MimeUtil::THEORA}};
+
+// List of codec IDs that are ambiguous and don't provide
+// enough information to determine the codec and profile.
+// The codec in these entries indicate the codec and profile
+// we assume the user is trying to indicate.
+static const CodecIDMappings kAmbiguousCodecStringMap[] = {
+    {"mp4a.40", MimeUtil::MPEG4_AAC_LC},
+    {"avc1", MimeUtil::H264_BASELINE},
+    {"avc3", MimeUtil::H264_BASELINE},
+    // avc1/avc3.XXXXXX may be ambiguous; handled by ParseH264CodecID().
+};
+
+MimeUtil::MimeUtil() : allow_proprietary_codecs_(false) {
+  InitializeMimeTypeMaps();
+}
+
+SupportsType MimeUtil::AreSupportedCodecs(
+    const CodecSet& supported_codecs,
+    const std::vector<std::string>& codecs) const {
+  DCHECK(!supported_codecs.empty());
+  DCHECK(!codecs.empty());
+
+  SupportsType result = IsSupported;
+  for (size_t i = 0; i < codecs.size(); ++i) {
+    bool is_ambiguous = true;
+    Codec codec = INVALID_CODEC;
+    if (!StringToCodec(codecs[i], &codec, &is_ambiguous))
+      return IsNotSupported;
+
+    if (!IsCodecSupported(codec) ||
+        supported_codecs.find(codec) == supported_codecs.end()) {
+      return IsNotSupported;
+    }
+
+    if (is_ambiguous)
+      result = MayBeSupported;
+  }
+
+  return result;
+}
+
+void MimeUtil::InitializeMimeTypeMaps() {
+  // Initialize the supported media types.
+  for (size_t i = 0; i < arraysize(common_media_types); ++i) {
+#if defined(OS_ANDROID)
+    if (!IsMimeTypeSupportedOnAndroid(common_media_types[i]))
+      continue;
+#endif
+    media_map_.insert(common_media_types[i]);
+  }
+#if defined(USE_PROPRIETARY_CODECS)
+  allow_proprietary_codecs_ = true;
+  for (size_t i = 0; i < arraysize(proprietary_media_types); ++i)
+    media_map_.insert(proprietary_media_types[i]);
+#endif
+
+  for (size_t i = 0; i < arraysize(kUnambiguousCodecStringMap); ++i) {
+    string_to_codec_map_[kUnambiguousCodecStringMap[i].codec_id] =
+        CodecEntry(kUnambiguousCodecStringMap[i].codec, false);
+  }
+
+  for (size_t i = 0; i < arraysize(kAmbiguousCodecStringMap); ++i) {
+    string_to_codec_map_[kAmbiguousCodecStringMap[i].codec_id] =
+        CodecEntry(kAmbiguousCodecStringMap[i].codec, true);
+  }
+
+  // Initialize the strict supported media types.
+  for (size_t i = 0; i < arraysize(format_codec_mappings); ++i) {
+    std::vector<std::string> mime_type_codecs;
+    ParseCodecString(format_codec_mappings[i].codecs_list,
+                     &mime_type_codecs,
+                     false);
+
+    CodecSet codecs;
+    for (size_t j = 0; j < mime_type_codecs.size(); ++j) {
+      Codec codec = INVALID_CODEC;
+      bool is_ambiguous = true;
+      CHECK(StringToCodec(mime_type_codecs[j], &codec, &is_ambiguous));
+      DCHECK(!is_ambiguous);
+      codecs.insert(codec);
+    }
+
+    strict_format_map_[format_codec_mappings[i].mime_type] = codecs;
+  }
+}
+
+bool MimeUtil::IsSupportedMediaMimeType(const std::string& mime_type) const {
+  return media_map_.find(base::StringToLowerASCII(mime_type)) !=
+         media_map_.end();
+}
+
+bool MimeUtil::AreSupportedMediaCodecs(
+    const std::vector<std::string>& codecs) const {
+  for (size_t i = 0; i < codecs.size(); ++i) {
+    Codec codec = INVALID_CODEC;
+    bool is_ambiguous = true;
+    if (!StringToCodec(codecs[i], &codec, &is_ambiguous) ||
+        !IsCodecSupported(codec)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+void MimeUtil::ParseCodecString(const std::string& codecs,
+                                std::vector<std::string>* codecs_out,
+                                bool strip) {
+  std::string no_quote_codecs;
+  base::TrimString(codecs, "\"", &no_quote_codecs);
+  base::SplitString(no_quote_codecs, ',', codecs_out);
+
+  if (!strip)
+    return;
+
+  // Strip everything past the first '.'
+  for (std::vector<std::string>::iterator it = codecs_out->begin();
+       it != codecs_out->end();
+       ++it) {
+    size_t found = it->find_first_of('.');
+    if (found != std::string::npos)
+      it->resize(found);
+  }
+}
+
+bool MimeUtil::IsStrictMediaMimeType(const std::string& mime_type) const {
+  return strict_format_map_.find(base::StringToLowerASCII(mime_type)) !=
+         strict_format_map_.end();
+}
+
+SupportsType MimeUtil::IsSupportedStrictMediaMimeType(
+    const std::string& mime_type,
+    const std::vector<std::string>& codecs) const {
+  const std::string mime_type_lower_case = base::StringToLowerASCII(mime_type);
+  StrictMappings::const_iterator it_strict_map =
+      strict_format_map_.find(mime_type_lower_case);
+  if (it_strict_map == strict_format_map_.end())
+    return codecs.empty() ? MayBeSupported : IsNotSupported;
+
+  if (it_strict_map->second.empty()) {
+    // We get here if the mimetype does not expect a codecs parameter.
+    return (codecs.empty() &&
+            IsDefaultCodecSupportedLowerCase(mime_type_lower_case))
+               ? IsSupported
+               : IsNotSupported;
+  }
+
+  if (codecs.empty()) {
+    // We get here if the mimetype expects to get a codecs parameter,
+    // but didn't get one. If |mime_type_lower_case| does not have a default
+    // codec the best we can do is say "maybe" because we don't have enough
+    // information.
+    Codec default_codec = INVALID_CODEC;
+    if (!GetDefaultCodecLowerCase(mime_type_lower_case, &default_codec))
+      return MayBeSupported;
+
+    return IsCodecSupported(default_codec) ? IsSupported : IsNotSupported;
+  }
+
+  return AreSupportedCodecs(it_strict_map->second, codecs);
+}
+
+void MimeUtil::RemoveProprietaryMediaTypesAndCodecsForTests() {
+  for (size_t i = 0; i < arraysize(proprietary_media_types); ++i) {
+    media_map_.erase(proprietary_media_types[i]);
+  }
+  allow_proprietary_codecs_ = false;
+}
+
+// Returns true iff |profile_str| conforms to hex string "42y0", where y is one
+// of [8..F]. Requiring constraint_set0_flag be set and profile_idc be 0x42 is
+// taken from ISO-14496-10 7.3.2.1, 7.4.2.1, and Annex A.2.1.
+//
+// |profile_str| is the first four characters of the H.264 suffix string
+// (ignoring the last 2 characters of the full 6 character suffix that are
+// level_idc). From ISO-14496-10 7.3.2.1, it consists of:
+// 8 bits: profile_idc: required to be 0x42 here.
+// 1 bit: constraint_set0_flag : required to be true here.
+// 1 bit: constraint_set1_flag : ignored here.
+// 1 bit: constraint_set2_flag : ignored here.
+// 1 bit: constraint_set3_flag : ignored here.
+// 4 bits: reserved : required to be 0 here.
+//
+// The spec indicates other ways, not implemented here, that a |profile_str|
+// can indicate a baseline conforming decoder is sufficient for decode in Annex
+// A.2.1: "[profile_idc not necessarily 0x42] with constraint_set0_flag set and
+// in which level_idc and constraint_set3_flag represent a level less than or
+// equal to the specified level."
+static bool IsValidH264BaselineProfile(const std::string& profile_str) {
+  uint32 constraint_set_bits;
+  if (profile_str.size() != 4 ||
+      profile_str[0] != '4' ||
+      profile_str[1] != '2' ||
+      profile_str[3] != '0' ||
+      !base::HexStringToUInt(base::StringPiece(profile_str.c_str() + 2, 1),
+                             &constraint_set_bits)) {
+    return false;
+  }
+
+  return constraint_set_bits >= 8;
+}
+
+static bool IsValidH264Level(const std::string& level_str) {
+  uint32 level;
+  if (level_str.size() != 2 || !base::HexStringToUInt(level_str, &level))
+    return false;
+
+  // Valid levels taken from Table A-1 in ISO-14496-10.
+  // Essentially |level_str| is toHex(10 * level).
+  return ((level >= 10 && level <= 13) ||
+          (level >= 20 && level <= 22) ||
+          (level >= 30 && level <= 32) ||
+          (level >= 40 && level <= 42) ||
+          (level >= 50 && level <= 51));
+}
+
+// Handle parsing H.264 codec IDs as outlined in RFC 6381 and ISO-14496-10.
+//   avc1.42y0xx, y >= 8 - H.264 Baseline
+//   avc1.4D40xx         - H.264 Main
+//   avc1.6400xx         - H.264 High
+//
+//   avc1.xxxxxx & avc3.xxxxxx are considered ambiguous forms that are trying to
+//   signal H.264 Baseline. For example, the idc_level, profile_idc and
+//   constraint_set3_flag pieces may explicitly require decoder to conform to
+//   baseline profile at the specified level (see Annex A and constraint_set0 in
+//   ISO-14496-10).
+static bool ParseH264CodecID(const std::string& codec_id,
+                             MimeUtil::Codec* codec,
+                             bool* is_ambiguous) {
+  // Make sure we have avc1.xxxxxx or avc3.xxxxxx
+  if (codec_id.size() != 11 ||
+      (!StartsWithASCII(codec_id, "avc1.", true) &&
+       !StartsWithASCII(codec_id, "avc3.", true))) {
+    return false;
+  }
+
+  std::string profile = StringToUpperASCII(codec_id.substr(5, 4));
+  if (IsValidH264BaselineProfile(profile)) {
+    *codec = MimeUtil::H264_BASELINE;
+  } else if (profile == "4D40") {
+    *codec = MimeUtil::H264_MAIN;
+  } else if (profile == "6400") {
+    *codec = MimeUtil::H264_HIGH;
+  } else {
+    *codec = MimeUtil::H264_BASELINE;
+    *is_ambiguous = true;
+    return true;
+  }
+
+  *is_ambiguous = !IsValidH264Level(StringToUpperASCII(codec_id.substr(9)));
+  return true;
+}
+
+bool MimeUtil::StringToCodec(const std::string& codec_id,
+                             Codec* codec,
+                             bool* is_ambiguous) const {
+  StringToCodecMappings::const_iterator itr =
+      string_to_codec_map_.find(codec_id);
+  if (itr != string_to_codec_map_.end()) {
+    *codec = itr->second.codec;
+    *is_ambiguous = itr->second.is_ambiguous;
+    return true;
+  }
+
+  // If |codec_id| is not in |string_to_codec_map_|, then we assume that it is
+  // an H.264 codec ID because currently those are the only ones that can't be
+  // stored in the |string_to_codec_map_| and require parsing.
+  return ParseH264CodecID(codec_id, codec, is_ambiguous);
+}
+
+bool MimeUtil::IsCodecSupported(Codec codec) const {
+  DCHECK_NE(codec, INVALID_CODEC);
+
+#if defined(OS_ANDROID)
+  if (!IsCodecSupportedOnAndroid(codec))
+    return false;
+#endif
+
+  return allow_proprietary_codecs_ || !IsCodecProprietary(codec);
+}
+
+bool MimeUtil::IsCodecProprietary(Codec codec) const {
+  switch (codec) {
+    case INVALID_CODEC:
+    case MP3:
+    case MPEG2_AAC_LC:
+    case MPEG2_AAC_MAIN:
+    case MPEG2_AAC_SSR:
+    case MPEG4_AAC_LC:
+    case MPEG4_AAC_SBR_v1:
+    case MPEG4_AAC_SBR_PS_v2:
+    case H264_BASELINE:
+    case H264_MAIN:
+    case H264_HIGH:
+      return true;
+
+    case PCM:
+    case VORBIS:
+    case OPUS:
+    case VP8:
+    case VP9:
+    case THEORA:
+      return false;
+  }
+
+  return true;
+}
+
+bool MimeUtil::GetDefaultCodecLowerCase(const std::string& mime_type_lower_case,
+                                        Codec* default_codec) const {
+  if (mime_type_lower_case == "audio/mpeg" ||
+      mime_type_lower_case == "audio/mp3" ||
+      mime_type_lower_case == "audio/x-mp3") {
+    *default_codec = MimeUtil::MP3;
+    return true;
+  }
+
+  return false;
+}
+
+bool MimeUtil::IsDefaultCodecSupportedLowerCase(
+    const std::string& mime_type_lower_case) const {
+  Codec default_codec = Codec::INVALID_CODEC;
+  if (!GetDefaultCodecLowerCase(mime_type_lower_case, &default_codec))
+    return false;
+  return IsCodecSupported(default_codec);
+}
+

[Ryan Sleevi, 2015/02/26 00:59:42]

Everything above here should be in an unnamed namespace to avoid any potential
ODR violations.

+bool IsSupportedMediaMimeType(const std::string& mime_type) {
+  return g_mime_util.Get().IsSupportedMediaMimeType(mime_type);
+}
+
+bool AreSupportedMediaCodecs(const std::vector<std::string>& codecs) {
+  return g_mime_util.Get().AreSupportedMediaCodecs(codecs);
+}
+
+bool IsStrictMediaMimeType(const std::string& mime_type) {
+  return g_mime_util.Get().IsStrictMediaMimeType(mime_type);
+}
+
+SupportsType IsSupportedStrictMediaMimeType(
+    const std::string& mime_type,
+    const std::vector<std::string>& codecs) {
+  return g_mime_util.Get().IsSupportedStrictMediaMimeType(mime_type, codecs);
+}
+
+void ParseCodecString(const std::string& codecs,
+                      std::vector<std::string>* codecs_out,
+                      const bool strip) {
+  g_mime_util.Get().ParseCodecString(codecs, codecs_out, strip);
+}
+
+void RemoveProprietaryMediaTypesAndCodecsForTests() {
+  g_mime_util.Get().RemoveProprietaryMediaTypesAndCodecsForTests();
+}
+
+}  // namespace media