Bug 1450607 - P1. Fix constness. r=gerald

MozReview-Commit-ID: CeftB0qmzTf

--HG--
extra : rebase_source : 7d8a75754990fd6cab1ad8f620d5d5675c46ea88

dom/media/MediaCache.cpp

@@ -2445,7 +2445,7 @@ MediaCacheStream::Unpin()
 }
 
 int64_t
-MediaCacheStream::GetLength()
+MediaCacheStream::GetLength() const
 {
   MOZ_ASSERT(!NS_IsMainThread());
   AutoLock lock(mMediaCache->Monitor());

dom/media/MediaCache.h

@@ -302,7 +302,7 @@ public:
   // the stream ended normally we return the length we actually got.
   // If we've successfully read data beyond the originally reported length,
   // we return the end of the data we've read.
-  int64_t GetLength();
+  int64_t GetLength() const;
   // Returns the unique resource ID. Call only on the main thread or while
   // holding the media cache lock.
   int64_t GetResourceID() { return mResourceID; }