Adding unittest for the reference counting of WebMediaStreamDescriptor/Source

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 # running overnight and removing outdated bugs/suppressions.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 5635 matching lines @@
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN9first_run8internal15LoadMasterPrefsEP8FilePath
    fun:_ZN8FirstRun24ProcessMasterPreferencesERK8FilePathPN9first_run11MasterPrefsE
    fun:_ZN22ChromeBrowserMainParts20PreCreateThreadsImplEv
    fun:_ZN22ChromeBrowserMainParts16PreCreateThreadsEv
    fun:_ZN7content15BrowserMainLoop23RunMainMessageLoopPartsEPb
    fun:_Z11BrowserMainRKN7content18MainFunctionParamsE
 }
 {
-   bug_111757
-   Memcheck:Leak
-   fun:malloc
-   fun:_ZN3WTF10fastMallocE*
-   ...
-   fun:_ZN7WebCore21MediaStreamDescriptor6createERKN3WTF6StringERKNS1_6VectorINS1_6RefPtrINS_17MediaStreamSourceEEEL*
-   fun:_ZN6WebKit24WebMediaStreamDescriptor10initializeERKNS_9WebStringERKNS_9WebVectorINS_20WebMediaStreamSourceEEE
-   fun:_ZN21PeerConnectionHandler28CreateWebKitStreamDescriptorEPN6webrtc20MediaStreamInterfaceE
-   fun:_ZN21PeerConnectionHandler19OnAddStreamCallbackEPN6webrtc20MediaStreamInterfaceE
-   fun:_ZN21PeerConnectionHandler11OnAddStreamEPN6webrtc20MediaStreamInterfaceE
-   fun:_ZN36PeerConnectionHandlerTest_Basic_Test8TestBodyEv
-}
-{
    bug_105580
    Memcheck:Leak
    fun:malloc_zone_malloc
    fun:malloc_set_zone_name
    fun:malloc_default_purgeable_zone
    ...
    fun:_ZN4base30EnableTerminationOnOutOfMemoryEv
    fun:_ZN7leveldb12_GLOBAL__N_111ChromiumEnvC2Ev
    fun:_ZN7leveldb12_GLOBAL__N_111ChromiumEnvC1Ev
    ...
@@ skipping 27 matching lines @@
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
 }
 {
    bug_todo_grep
    Memcheck:Leak
    fun:malloc
    obj:/bin/grep
    obj:/bin/grep
 }