Bug 1361964 - WebMBufferedState::UpdateIndex() should read from cache. r=jya

We don't want to trigger download when calculating buffer ranges since download
changes buffer ranges.

MozReview-Commit-ID: Be8qFUQ5PpR

--HG--
extra : rebase_source : 4fd77e031577332d9d112faef869cd935275b1af

dom/media/MediaResource.h

@@ -242,6 +242,17 @@ public:
     return bytes.forget();
   }
 
+  already_AddRefed<MediaByteBuffer> CachedReadAt(int64_t aOffset, uint32_t aCount)
+  {
+    RefPtr<MediaByteBuffer> bytes = new MediaByteBuffer();
+    bool ok = bytes->SetLength(aCount, fallible);
+    NS_ENSURE_TRUE(ok, nullptr);
+    char* curr = reinterpret_cast<char*>(bytes->Elements());
+    nsresult rv = ReadFromCache(curr, aOffset, aCount);
+    NS_ENSURE_SUCCESS(rv, nullptr);
+    return bytes.forget();
+  }
+
   // Report the current offset in bytes from the start of the stream.
   // This is used to approximate where we currently are in the playback of a
   // media.

dom/media/webm/WebMBufferedParser.cpp

@@ -449,7 +449,7 @@ void WebMBufferedState::UpdateIndex(const MediaByteRangeSet& aRanges, MediaResou
     while (length > 0) {
       static const uint32_t BLOCK_SIZE = 1048576;
       uint32_t block = std::min(length, BLOCK_SIZE);
-      RefPtr<MediaByteBuffer> bytes = aResource->MediaReadAt(offset, block);
+      RefPtr<MediaByteBuffer> bytes = aResource->CachedReadAt(offset, block);
       if (!bytes) {
         break;
       }