Factor out authorization from AudioRendererHost.

content/browser/renderer_host/media/media_stream_manager.cc

Index: content/browser/renderer_host/media/media_stream_manager.cc
diff --git a/content/browser/renderer_host/media/media_stream_manager.cc b/content/browser/renderer_host/media/media_stream_manager.cc
index 28fd3dfd9da939c95de268b7bff8135763cc41dd..9100ab2eb5a0a5a07c172a40b9d1865dd93fc3d5 100644
--- a/content/browser/renderer_host/media/media_stream_manager.cc
+++ b/content/browser/renderer_host/media/media_stream_manager.cc
@@ -1970,6 +1970,21 @@ bool MediaStreamManager::DoesMediaDeviceIDMatchHMAC(
 }
 
 // static
+bool MediaStreamManager::IsValidDeviceId(const std::string& device_id) {

[o1ka, 2016/11/03 10:07:22]

What is the reason for MediaStreaMgr to expose it? Isn't it enough oi have it in
media_device_id?

[Max Morin, 2016/11/10 14:59:52]

I figured I'd put it with the rest of the hashing-related functions, but I've
moved it to media_device_id now.

+  constexpr int hash_size = 64;  // 32 bytes * 2 char/byte hex encoding
+  if (media::AudioDeviceDescription::IsDefaultDevice(device_id) ||
+      device_id == media::AudioDeviceDescription::kCommunicationsDeviceId)
+    return true;
+
+  if (device_id.length() != hash_size)
+    return false;
+
+  return std::all_of(device_id.cbegin(), device_id.cend(), [](const char& c) {
+    return base::IsAsciiLower(c) || base::IsAsciiDigit(c);
+  });
+}
+
+// static
 bool MediaStreamManager::IsOriginAllowed(int render_process_id,
                                          const url::Origin& origin) {
   if (!ChildProcessSecurityPolicyImpl::GetInstance()->CanRequestURL(