Assertion when reloading webm video: ASSERT(!m_parseTracksStatus);

[Jean-Yves Avenard [:jya]]

STR:
In a debug build:
- Load http://cali.apple.com/qadrift/_media/_streams/webM/source_files/vp8/Big_Buck_Bunny_4K.webm.480p.webm
- Refresh the page

Assertion ASSERT(!m_parseTracksStatus); in MediaFormatReader::didParseTracks

```
lldb) bt
* thread #28, queue = 'WebKit::MediaFormatReader Queue', stop reason = EXC_BAD_ACCESS (code=1, address=0xbbadbeef)
    frame #0: 0x000000013322cafc JavaScriptCore`::WTFCrash() at Assertions.cpp:322:35
    frame #1: 0x000000011857bda4 WebKit`WTFCrashWithInfo((null)=188, (null)="/Users/jyavenard/Work/webkit/OpenSource/Source/WebKit/Shared/mac/MediaFormatReader/MediaFormatReader.cpp", (null)="void WebKit::MediaFormatReader::didParseTracks(SourceBufferPrivateClient::InitializationSegment &&, uint64_t)", (null)=2723) at Assertions.h:732:5
  * frame #2: 0x000000011898f258 WebKit`WebKit::MediaFormatReader::didParseTracks(this=0x0000600000cc9220, segment=0x000000016d072700, errorCode=2008) at MediaFormatReader.cpp:188:5
    frame #3: 0x000000011899d2e0 WebKit`WebKit::MediaFormatReader::parseByteSource(this=0x0000000106004108, errorCode=2008)::$_4::operator()(unsigned long long) const at MediaFormatReader.cpp:162:9
    frame #4: 0x000000011899d1a0 WebKit`WTF::Detail::CallableWrapper<WebKit::MediaFormatReader::parseByteSource(WTF::RetainPtr<OpaqueMTPluginByteSource*>&&)::$_4, void, unsigned long long>::call(this=0x0000000106004100, in=2008) at Function.h:53:39
    frame #5: 0x00000001482d1568 WebCore`WTF::Function<void (unsigned long long)>::operator(this=0x0000000106078220, in=2008)(unsigned long long) const at Function.h:82:35
    frame #6: 0x000000014aa040fc WebCore`WebCore::SourceBufferParserWebM::appendData(this=0x000000010613c0c8)>&&, WebCore::SourceBufferParser::AppendFlags)::$_11::operator()() const at SourceBufferParserWebM.cpp:749:13
    frame #7: 0x000000014aa03e50 WebCore`WTF::Detail::CallableWrapper<WebCore::SourceBufferParserWebM::appendData(WebCore::SourceBufferParser::Segment&&, WTF::CompletionHandler<void ()>&&, WebCore::SourceBufferParser::AppendFlags)::$_11, void>::call(this=0x000000010613c0c0) at Function.h:53:39
    frame #8: 0x00000001332542b0 JavaScriptCore`WTF::Function<void ()>::operator(this=0x0000000106008228)() const at Function.h:82:35
    frame #9: 0x00000001333794b8 JavaScriptCore`WTF::(anonymous namespace)::DispatchWorkItem::operator(this=0x0000000106008220)() at WorkQueueCocoa.cpp:40:25
    frame #10: 0x0000000133377d54 JavaScriptCore`void WTF::dispatchWorkItem<WTF::(anonymous namespace)::DispatchWorkItem>(dispatchContext=0x0000000106008220) at WorkQueueCocoa.cpp:48:5
    frame #11: 0x000000010347e480 libdispatch.dylib`_dispatch_client_callout + 20
    frame #12: 0x0000000103487834 libdispatch.dylib`_dispatch_lane_serial_drain + 980
    frame #13: 0x000000010348889c libdispatch.dylib`_dispatch_lane_invoke + 440
    frame #14: 0x0000000103498184 libdispatch.dylib`_dispatch_workloop_worker_thread + 1232
    frame #15: 0x000000010307fef4 libsystem_pthread.dylib`_pthread_wqthread + 288
(lldb) 
```

[Jean-Yves Avenard [:jya]]

This started with bug 232740 as now an error can be returned while reading, which causes an error to be emitted and the error handler will call didParseTracks() again

[Radar WebKit Bug Importer]

<rdar://problem/86706195>