FileAPI: Fix memory leak in WebFileSystemImpl (won't commit)

tools/valgrind/memcheck/suppressions.txt

 # There are four kinds of suppressions in this file.
 # 1. third party stuff we have no control over
 #
 # 2. intentional unit test errors, or stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing
 #
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system (but a few aren't yet).
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 5866 matching lines @@
 {
    bug_293033
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN7WebCore11ScriptState10forContextEN2v86HandleINS1_7ContextEEE
    ...
    fun:_ZN7WebCore*V8InternalL*MethodERKN2v820FunctionCallbackInfoINS1_5ValueEEE
    fun:_ZN7WebCore*V8InternalL*MethodCallbackERKN2v820FunctionCallbackInfoINS1_5ValueEEE
 }
 {
-   bug_293058_a
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN7content12_GLOBAL__N_123WaitableCallbackResultsC1Ev
-   fun:_ZN7content12_GLOBAL__N_123WaitableCallbackResults11MaybeCreateERKN5blink22WebFileSystemCallbacksE
-   fun:_ZN7content17WebFileSystemImpl*
-}
-{
-   bug_293058_b
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN7content12_GLOBAL__N_123WaitableCallbackResultsC1Ev
-   fun:_ZN7content12_GLOBAL__N_123WaitableCallbackResults11MaybeCreateERKN5blink22WebFileSystemCallbacksE
-   fun:_ZN7content17WebFileSystemImpl16createFileWriterERKN5blink6WebURLEPNS1_19WebFileWriterClientENS1_22WebFileSystemCallbacksE
-   fun:_ZN7WebCore17DOMFileSystemSync12createWriterEPKNS_13FileEntrySyncERNS_14ExceptionStateE
-   fun:_ZN7WebCore13FileEntrySync12createWriterERNS_14ExceptionStateE
-}
-{
    bug_293088
    Memcheck:Unaddressable
    fun:_ZNK3WTF6RefPtrIN7WebCore19TextResourceDecoderEE3getEv
    fun:_ZNK7WebCore8Document7decoderEv
    fun:_ZN7WebCore25DecodedDataDocumentParser5flushEv
    fun:_ZN7WebCore14DocumentWriter3endEv
    fun:_ZN7WebCore14DocumentLoader10endWritingEPNS_14DocumentWriterE
    fun:_ZN7WebCore14DocumentLoader15finishedLoadingEd
    fun:_ZN7WebCore14DocumentLoader14notifyFinishedEPNS_8ResourceE
    fun:_ZN7WebCore8Resource11checkNotifyEv
@@ skipping 423 matching lines @@
    fun:_ZN3WTFL19wtfThreadEntryPointEPv
 }
 {
    bug_349152
    Memcheck:Uninitialized
    ...
    fun:_ZN7content31MediaStreamAudioLevelCalculator9CalculateEPKsii
    fun:_ZN7content21WebRtcLocalAudioTrack7CaptureEPKsN4base9TimeDeltaEibb
    fun:_ZN7content54WebRtcLocalAudioTrackAdapterTest_AddAndRemoveSink_Test8TestBodyEv
 }