Cast: Increase max outstanding frames to 120

Max outstanding frame used to be 60 to work around an issue with 8-bits
integer wrap around for frame IDs. Now the logic for handling wrap
around us less buggy we can increase the limit to 120 frames.

TBR=hubbe

Review URL: https://codereview.chromium.org/476303004

Cr-Commit-Position: refs/heads/master@{#290126}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290126 0039d316-1c4b-4281-b951-d872f2087c98

media/cast/cast_defines.h

@@ -27,7 +27,10 @@ const uint32 kStartFrameId = UINT32_C(0xffffffff);
 // This is an important system-wide constant.  This limits how much history the
 // implementation must retain in order to process the acknowledgements of past
 // frames.
-const int kMaxUnackedFrames = 60;
+// This value is carefully choosen such that it fits in the 8-bits range for
+// frame IDs. It is also less than half of the full 8-bits range such that we
+// can handle wrap around and compare two frame IDs.
+const int kMaxUnackedFrames = 120;
 
 const int kStartRttMs = 20;
 const int64 kCastMessageUpdateIntervalMs = 33;